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* Octave: (octave).             Interactive language for numerical computations.
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File: octave.info,  Node: Filesystem Utilities,  Next: File Archiving Utilities,  Prev: Timing Utilities,  Up: System Utilities

36.2 Filesystem Utilities
=========================

Octave includes many utility functions for copying, moving, renaming,
and deleting files; for creating, reading, and deleting directories; for
retrieving status information on files; and for manipulating file and
path names.

 -- : movefile F1
 -- : movefile F1 F2
 -- : movefile F1 F2 f
 -- : movefile (F1)
 -- : movefile (F1, F2)
 -- : movefile (F1, F2, 'f')
 -- : [STATUS, MSG, MSGID] = movefile (...)
     Move the source file or directory F1 to the destination F2.

     The name F1 may contain globbing patterns, or may be a cell array
     of strings.  If F1 expands to multiple filenames, F2 must be a
     directory.

     If no destination F2 is specified then the destination is the
     present working directory.  If F2 is a filename then F1 is renamed
     to F2.

     When the force flag ’f’ is given any existing files will be
     overwritten without prompting.

     If successful, STATUS is 1, and MSG, MSGID are empty character
     strings ("").  Otherwise, STATUS is 0, MSG contains a
     system-dependent error message, and MSGID contains a unique message
     identifier.  Note that the status code is exactly opposite that of
     the ‘system’ command.

     See also: *note rename: XREFrename, *note copyfile: XREFcopyfile,
     *note unlink: XREFunlink, *note delete: XREFdelete, *note glob:
     XREFglob.

 -- : rename OLD NEW
 -- : [ERR, MSG] = rename (OLD, NEW)
     Change the name of file OLD to NEW.

     If successful, ERR is 0 and MSG is an empty string.  Otherwise, ERR
     is nonzero and MSG contains a system-dependent error message.

     See also: *note movefile: XREFmovefile, *note copyfile:
     XREFcopyfile, *note ls: XREFls, *note dir: XREFdir.

 -- : copyfile F1 F2
 -- : copyfile F1 F2 f
 -- : copyfile (F1, F2)
 -- : copyfile (F1, F2, 'f')
 -- : [STATUS, MSG, MSGID] = copyfile (...)
     Copy the source file(s) or directory F1 to the destination F2.

     The name F1 may contain globbing patterns, or may be a cell array
     of strings.  If F1 expands to multiple filenames, F2 must be a
     directory.

     When the force flag ’f’ is given any existing files will be
     overwritten without prompting.

     If successful, STATUS is 1, and MSG, MSGID are empty character
     strings ("").  Otherwise, STATUS is 0, MSG contains a
     system-dependent error message, and MSGID contains a unique message
     identifier.  Note that the status code is exactly opposite that of
     the ‘system’ command.

     See also: *note movefile: XREFmovefile, *note rename: XREFrename,
     *note unlink: XREFunlink, *note delete: XREFdelete, *note glob:
     XREFglob.

 -- : [ERR, MSG] = unlink (FILE)
     Delete the file named FILE.

     If successful, ERR is 0 and MSG is an empty string.  Otherwise, ERR
     is nonzero and MSG contains a system-dependent error message.

     See also: *note delete: XREFdelete, *note rmdir: XREFrmdir.

 -- : link OLD NEW
 -- : [ERR, MSG] = link (OLD, NEW)
     Create a new link (also known as a hard link) to an existing file.

     If successful, ERR is 0 and MSG is an empty string.  Otherwise, ERR
     is nonzero and MSG contains a system-dependent error message.

     See also: *note symlink: XREFsymlink, *note unlink: XREFunlink,
     *note readlink: XREFreadlink, *note lstat: XREFlstat.

 -- : symlink OLD NEW
 -- : [ERR, MSG] = symlink (OLD, NEW)
     Create a symbolic link NEW which contains the string OLD.

     If successful, ERR is 0 and MSG is an empty string.  Otherwise, ERR
     is nonzero and MSG contains a system-dependent error message.

     See also: *note link: XREFlink, *note unlink: XREFunlink, *note
     readlink: XREFreadlink, *note lstat: XREFlstat.

 -- : readlink SYMLINK
 -- : [RESULT, ERR, MSG] = readlink (SYMLINK)
     Read the value of the symbolic link SYMLINK.

     If successful, RESULT contains the contents of the symbolic link
     SYMLINK, ERR is 0, and MSG is an empty string.  Otherwise, ERR is
     nonzero and MSG contains a system-dependent error message.

     See also: *note lstat: XREFlstat, *note symlink: XREFsymlink, *note
     link: XREFlink, *note unlink: XREFunlink, *note delete: XREFdelete.

 -- : mkdir DIRNAME
 -- : mkdir PARENT DIRNAME
 -- : mkdir (DIRNAME)
 -- : mkdir (PARENT, DIRNAME)
 -- : [STATUS, MSG, MSGID] = mkdir (...)
     Create a directory named DIRNAME in the directory PARENT, creating
     any intermediate directories if necessary.

     If DIRNAME is a relative path, and no PARENT directory is
     specified, then the present working directory is used.

     If successful, STATUS is 1, and MSG and MSGID are empty strings
     ("").  Otherwise, STATUS is 0, MSG contains a system-dependent
     error message, and MSGID contains a unique message identifier.

     When creating a directory permissions will be set to
     ‘0777 - UMASK’.

     See also: *note rmdir: XREFrmdir, *note pwd: XREFpwd, *note cd:
     XREFcd, *note umask: XREFumask.

 -- : rmdir DIR
 -- : rmdir (DIR, "s")
 -- : [STATUS, MSG, MSGID] = rmdir (...)
     Remove the directory named DIR.

     If the optional second parameter is supplied with value "s",
     recursively remove all subdirectories as well.

     If successful, STATUS is 1, and MSG, MSGID are empty character
     strings ("").  Otherwise, STATUS is 0, MSG contains a
     system-dependent error message, and MSGID contains a unique message
     identifier.

     See also: *note mkdir: XREFmkdir, *note confirm_recursive_rmdir:
     XREFconfirm_recursive_rmdir, *note pwd: XREFpwd.

 -- : VAL = confirm_recursive_rmdir ()
 -- : OLD_VAL = confirm_recursive_rmdir (NEW_VAL)
 -- : confirm_recursive_rmdir (NEW_VAL, "local")
     Query or set the internal variable that controls whether Octave
     will ask for confirmation before recursively removing a directory
     tree.

     When called from inside a function with the "local" option, the
     variable is changed locally for the function and any subroutines it
     calls.  The original variable value is restored when exiting the
     function.

     See also: *note rmdir: XREFrmdir.

 -- : ERR = mkfifo (NAME, MODE)
 -- : [ERR, MSG] = mkfifo (NAME, MODE)
     Create a FIFO special file named NAME with file mode MODE.

     MODE is interpreted as an octal number and is subject to umask
     processing.  The final calculated mode is ‘MODE - UMASK’.

     If successful, ERR is 0 and MSG is an empty string.  Otherwise, ERR
     is nonzero and MSG contains a system-dependent error message.

     See also: *note pipe: XREFpipe, *note umask: XREFumask.

 -- : umask (MASK)
     Set the permission mask for file creation.

     The parameter MASK is an integer, interpreted as an octal number.

     If successful, returns the previous value of the mask (as an
     integer to be interpreted as an octal number); otherwise an error
     message is printed.

     The permission mask is a UNIX concept used when creating new
     objects on a file system such as files, directories, or named
     FIFOs.  The object to be created has base permissions in an octal
     number MODE which are modified according to the octal value of
     MASK.  The final permissions for the new object are ‘MODE - MASK’.

     See also: *note fopen: XREFfopen, *note mkdir: XREFmkdir, *note
     mkfifo: XREFmkfifo.

 -- : [INFO, ERR, MSG] = stat (FILE)
 -- : [INFO, ERR, MSG] = stat (FID)
 -- : [INFO, ERR, MSG] = lstat (FILE)
 -- : [INFO, ERR, MSG] = lstat (FID)
     Return a structure INFO containing the following information about
     FILE or file identifier FID.

     ‘dev’
          ID of device containing a directory entry for this file.

     ‘ino’
          File number of the file.

     ‘mode’
          File mode, as an integer.  Use the functions ‘S_ISREG’,
          ‘S_ISDIR’, ‘S_ISCHR’, ‘S_ISBLK’, ‘S_ISFIFO’, ‘S_ISLNK’, or
          ‘S_ISSOCK’ to extract information from this value.

     ‘modestr’
          File mode, as a string of ten letters or dashes as would be
          returned by ‘ls -l’.

     ‘nlink’
          Number of links.

     ‘uid’
          User ID of file’s owner.

     ‘gid’
          Group ID of file’s group.

     ‘rdev’
          ID of device for block or character special files.

     ‘size’
          Size in bytes.

     ‘atime’
          Time of last access in the same form as time values returned
          from ‘time’.  *Note Timing Utilities::.

     ‘mtime’
          Time of last modification in the same form as time values
          returned from ‘time’.  *Note Timing Utilities::.

     ‘ctime’
          Time of last file status change in the same form as time
          values returned from ‘time’.  *Note Timing Utilities::.

     ‘blksize’
          Size of blocks in the file.

     ‘blocks’
          Number of blocks allocated for file.

     If the call is successful ERR is 0 and MSG is an empty string.  If
     the file does not exist, or some other error occurs, INFO is an
     empty matrix, ERR is −1, and MSG contains the corresponding system
     error message.

     If FILE is a symbolic link, ‘stat’ will return information about
     the actual file that is referenced by the link.  Use ‘lstat’ if you
     want information about the symbolic link itself.

     For example:

          [info, err, msg] = stat ("/vmlinuz")
            ⇒ info =
               {
                 atime = 855399756
                 rdev = 0
                 ctime = 847219094
                 uid = 0
                 size = 389218
                 blksize = 4096
                 mtime = 847219094
                 gid = 6
                 nlink = 1
                 blocks = 768
                 mode = -rw-r--r--
                 modestr = -rw-r--r--
                 ino = 9316
                 dev = 2049
               }
            ⇒ err = 0
            ⇒ msg =

     See also: *note lstat: XREFlstat, *note ls: XREFls, *note dir:
     XREFdir, *note isfile: XREFisfile, *note isfolder: XREFisfolder.

 -- : S_ISBLK (MODE)
     Return true if MODE corresponds to a block device.

     The value of MODE is assumed to be returned from a call to ‘stat’.

     See also: *note stat: XREFstat, *note lstat: XREFlstat.

 -- : S_ISCHR (MODE)
     Return true if MODE corresponds to a character device.

     The value of MODE is assumed to be returned from a call to ‘stat’.

     See also: *note stat: XREFstat, *note lstat: XREFlstat.

 -- : S_ISDIR (MODE)
     Return true if MODE corresponds to a directory.

     The value of MODE is assumed to be returned from a call to ‘stat’.

     See also: *note stat: XREFstat, *note lstat: XREFlstat.

 -- : S_ISFIFO (MODE)
     Return true if MODE corresponds to a fifo.

     The value of MODE is assumed to be returned from a call to ‘stat’.

     See also: *note stat: XREFstat, *note lstat: XREFlstat.

 -- : S_ISLNK (MODE)
     Return true if MODE corresponds to a symbolic link.

     The value of MODE is assumed to be returned from a call to ‘stat’.

     See also: *note stat: XREFstat, *note lstat: XREFlstat.

 -- : S_ISREG (MODE)
     Return true if MODE corresponds to a regular file.

     The value of MODE is assumed to be returned from a call to ‘stat’.

     See also: *note stat: XREFstat, *note lstat: XREFlstat.

 -- : S_ISSOCK (MODE)
     Return true if MODE corresponds to a socket.

     The value of MODE is assumed to be returned from a call to ‘stat’.

     See also: *note stat: XREFstat, *note lstat: XREFlstat.

 -- : fileattrib (FILE)
 -- : fileattrib ()
 -- : [STATUS, MSG, MSGID] = fileattrib (...)
     Return information about FILE.

     If successful, STATUS is 1 and MSG is a structure with the
     following fields:

     ‘Name’
          Full name of FILE.

     ‘archive’
          True if FILE is an archive (Windows).

     ‘system’
          True if FILE is a system file (Windows).

     ‘hidden’
          True if FILE is a hidden file (Windows).

     ‘directory’
          True if FILE is a directory.

     ‘UserRead’
     ‘GroupRead’
     ‘OtherRead’
          True if the user (group; other users) has read permission for
          FILE.

     ‘UserWrite’
     ‘GroupWrite’
     ‘OtherWrite’
          True if the user (group; other users) has write permission for
          FILE.

     ‘UserExecute’
     ‘GroupExecute’
     ‘OtherExecute’
          True if the user (group; other users) has execute permission
          for FILE.

     If an attribute does not apply (i.e., archive on a Unix system)
     then the field is set to NaN.

     If ‘attrib’ fails, MSG is a non-empty string containing an error
     message and MSG_ID is the non-empty string "fileattrib".

     With no input arguments, return information about the current
     directory.

     If FILE contains globbing characters, return information about all
     the matching files.

     See also: *note glob: XREFglob.

 -- : TF = isfile (F)
     Return true if F is a regular file and false otherwise.

     If F is a cell array of strings, TF is a logical array of the same
     size.

     See also: *note isfolder: XREFisfolder, *note exist: XREFexist,
     *note stat: XREFstat, *note is_absolute_filename:
     XREFis_absolute_filename, *note is_rooted_relative_filename:
     XREFis_rooted_relative_filename.

 -- : isdir (F)

     This function is not recommended.  Use ‘isfolder’ or
     ‘file_in_loadpath’ instead.

     Return true if F is a directory and false otherwise.

     Compatibility Note: The MATLAB function of the same name will also
     search for F in the load path directories.  To emulate this
     behavior use

          TF = ! isempty (file_in_loadpath (F))

     See also: *note isfolder: XREFisfolder, *note file_in_loadpath:
     XREFfile_in_loadpath, *note exist: XREFexist, *note stat: XREFstat,
     *note is_absolute_filename: XREFis_absolute_filename, *note
     is_rooted_relative_filename: XREFis_rooted_relative_filename.

 -- : isfolder (F)
 -- : TF = isfolder (F)
     Return true if F is a directory and false otherwise.

     If F is a cell array of strings, TF is a logical array of the same
     size.

     See also: *note isfile: XREFisfile, *note exist: XREFexist, *note
     stat: XREFstat, *note is_absolute_filename:
     XREFis_absolute_filename, *note is_rooted_relative_filename:
     XREFis_rooted_relative_filename.

 -- : FILES = readdir (DIR)
 -- : [FILES, ERR, MSG] = readdir (DIR)
     Return the names of files in the directory DIR as a cell array of
     strings.

     If an error occurs, return an empty cell array in FILES.  If
     successful, ERR is 0 and MSG is an empty string.  Otherwise, ERR is
     nonzero and MSG contains a system-dependent error message.

     See also: *note ls: XREFls, *note dir: XREFdir, *note glob:
     XREFglob, *note what: XREFwhat.

 -- : glob (PATTERN)
     Given an array of pattern strings (as a char array or a cell array)
     in PATTERN, return a cell array of filenames that match any of
     them, or an empty cell array if no patterns match.

     The pattern strings are interpreted as filename globbing patterns
     (as they are used by Unix shells).

     Within a pattern

     ‘*’
          matches any string, including the null string,

     ‘?’
          matches any single character, and

     ‘[...]’
          matches any of the enclosed characters.

     Tilde expansion is performed on each of the patterns before looking
     for matching filenames.  For example:

          ls
             ⇒
                file1  file2  file3  myfile1 myfile1b
          glob ("*file1")
             ⇒
                {
                  [1,1] = file1
                  [2,1] = myfile1
                }
          glob ("myfile?")
             ⇒
                {
                  [1,1] = myfile1
                }
          glob ("file[12]")
             ⇒
                {
                  [1,1] = file1
                  [2,1] = file2
                }

     See also: *note ls: XREFls, *note dir: XREFdir, *note readdir:
     XREFreaddir, *note what: XREFwhat.

 -- : file_in_path (PATH, FILE)
 -- : file_in_path (PATH, FILE, "all")
     Return the absolute name of FILE if it can be found in PATH.

     The value of PATH should be a colon-separated list of directories
     in the format described for ‘path’.  If no file is found, return an
     empty character string.  For example:

          file_in_path (EXEC_PATH, "sh")
               ⇒ "/bin/sh"

     If the second argument is a cell array of strings, search each
     directory of the path for element of the cell array and return the
     first that matches.

     If the third optional argument "all" is supplied, return a cell
     array containing the list of all files that have the same name in
     the path.  If no files are found, return an empty cell array.

     See also: *note file_in_loadpath: XREFfile_in_loadpath, *note
     dir_in_loadpath: XREFdir_in_loadpath, *note path: XREFpath.

 -- : filesep ()
 -- : filesep ("all")
     Return the system-dependent character used to separate directory
     names.

     If "all" is given, the function returns all valid file separators
     in the form of a string.  The list of file separators is
     system-dependent.  It is ‘/’ (forward slash) under UNIX or
     Mac OS X, ‘/’ and ‘\’ (forward and backward slashes) under Windows.

     See also: *note pathsep: XREFpathsep.

 -- : [DIR, NAME, EXT] = fileparts (FILENAME)
     Return the directory, name, and extension components of FILENAME.

     The input FILENAME is a string which is parsed.  There is no
     attempt to check whether the filename or directory specified
     actually exists.

     See also: *note fullfile: XREFfullfile, *note filesep: XREFfilesep.

 -- : FILENAME = fullfile (DIR1, DIR2, ..., FILE)
 -- : FILENAMES = fullfile (..., FILES)
     Build complete filename from separate parts.

     Joins any number of path components intelligently.  The return
     value is the concatenation of each component with exactly one file
     separator between each non empty part and at most one leading
     and/or trailing file separator.

     If the last component part is a cell array, returns a cell array of
     filepaths, one for each element in the last component, e.g.:

          fullfile ("/home/username", "data", {"f1.csv", "f2.csv", "f3.csv"})
            ⇒
                {
                  [1,1] = /home/username/data/f1.csv
                  [1,2] = /home/username/data/f2.csv
                  [1,3] = /home/username/data/f3.csv
                }

     On Windows systems, while forward slash file separators do work,
     they are replaced by backslashes; in addition drive letters are
     stripped of leading file separators to obtain a valid file path.

     Note: ‘fullfile’ does not perform any validation of the resulting
     full filename.

     See also: *note fileparts: XREFfileparts, *note filesep:
     XREFfilesep.

 -- : tilde_expand (STRING)
 -- : tilde_expand (CELLSTR)
     Perform tilde expansion on STRING.

     If STRING begins with a tilde character, (‘~’), all of the
     characters preceding the first slash (or all characters, if there
     is no slash) are treated as a possible user name, and the tilde and
     the following characters up to the slash are replaced by the home
     directory of the named user.  If the tilde is followed immediately
     by a slash, the tilde is replaced by the home directory of the user
     running Octave.

     If the input is a cell array of strings CELLSTR then tilde
     expansion is performed on each string element.

     Examples:

          tilde_expand ("~joeuser/bin")
               ⇒ "/home/joeuser/bin"
          tilde_expand ("~/bin")
               ⇒ "/home/jwe/bin"

 -- : [CNAME, STATUS, MSG] = canonicalize_file_name (FNAME)
     Return the canonical name of file FNAME.

     If the file does not exist the empty string ("") is returned.

     See also: *note make_absolute_filename: XREFmake_absolute_filename,
     *note is_absolute_filename: XREFis_absolute_filename, *note
     is_rooted_relative_filename: XREFis_rooted_relative_filename.

 -- : make_absolute_filename (FILE)
     Return the full name of FILE beginning from the root of the file
     system.

     No check is done for the existence of FILE.

     See also: *note canonicalize_file_name: XREFcanonicalize_file_name,
     *note is_absolute_filename: XREFis_absolute_filename, *note
     is_rooted_relative_filename: XREFis_rooted_relative_filename, *note
     isfolder: XREFisfolder.

 -- : is_absolute_filename (FILE)
     Return true if FILE is an absolute filename.

     See also: *note is_rooted_relative_filename:
     XREFis_rooted_relative_filename, *note make_absolute_filename:
     XREFmake_absolute_filename, *note isfolder: XREFisfolder.

 -- : is_rooted_relative_filename (FILE)
     Return true if FILE is a rooted-relative filename.

     See also: *note is_absolute_filename: XREFis_absolute_filename,
     *note make_absolute_filename: XREFmake_absolute_filename, *note
     isfolder: XREFisfolder.

 -- : VAL = recycle ()
 -- : OLD_VAL = recycle (NEW_VAL)
     Query or set the preference for recycling deleted files.

     When recycling is enabled, commands which would permanently erase
     files instead move them to a temporary location (such as the
     directory labeled Trash).

     Programming Note: This function is provided for MATLAB
     compatibility, but recycling is not implemented in Octave.  To help
     avoid accidental data loss an error will be raised if an attempt is
     made to enable file recycling.

     See also: *note delete: XREFdelete, *note rmdir: XREFrmdir.


File: octave.info,  Node: File Archiving Utilities,  Next: Networking Utilities,  Prev: Filesystem Utilities,  Up: System Utilities

36.3 File Archiving Utilities
=============================

 -- : bunzip2 (BZFILE)
 -- : bunzip2 (BZFILE, DIR)
 -- : FILELIST = bunzip2 (...)
     Unpack the bzip2 archive BZFILE.

     If DIR is specified the files are unpacked in this directory rather
     than the one where BZFILE is located.

     The optional output FILELIST is a list of the uncompressed files.

     See also: *note bzip2: XREFbzip2, *note unpack: XREFunpack, *note
     gunzip: XREFgunzip, *note unzip: XREFunzip, *note untar: XREFuntar.

 -- : FILELIST = gzip (FILES)
 -- : FILELIST = gzip (FILES, DIR)
     Compress the list of files and directories specified in FILES.

     FILES is a character array or cell array of strings.  Shell
     wildcards in the filename such as ‘*’ or ‘?’ are accepted and
     expanded.  Each file is compressed separately and a new file with a
     ‘".gz"’ extension is created.  The original files are not modified,
     but existing compressed files will be silently overwritten.  If a
     directory is specified then ‘gzip’ recursively compresses all files
     in the directory.

     If DIR is defined the compressed files are placed in this
     directory, rather than the original directory where the
     uncompressed file resides.  Note that this does not replicate a
     directory tree in DIR which may lead to files overwriting each
     other if there are multiple files with the same name.

     If DIR does not exist it is created.

     The optional output FILELIST is a list of the compressed files.

     See also: *note gunzip: XREFgunzip, *note unpack: XREFunpack, *note
     bzip2: XREFbzip2, *note zip: XREFzip, *note tar: XREFtar.

 -- : gunzip (GZFILE)
 -- : gunzip (GZFILE, DIR)
 -- : FILELIST = gunzip (...)
     Unpack the gzip archive GZFILE.

     If GZFILE is a directory, all gzfiles in the directory will be
     recursively unpacked.

     If DIR is specified the files are unpacked in this directory rather
     than the one where GZFILE is located.

     The optional output FILELIST is a list of the uncompressed files.

     See also: *note gzip: XREFgzip, *note unpack: XREFunpack, *note
     bunzip2: XREFbunzip2, *note unzip: XREFunzip, *note untar:
     XREFuntar.

 -- : FILELIST = tar (TARFILE, FILES)
 -- : FILELIST = tar (TARFILE, FILES, ROOTDIR)
     Pack the list of files and directories specified in FILES into the
     TAR archive TARFILE.

     FILES is a character array or cell array of strings.  Shell
     wildcards in the filename such as ‘*’ or ‘?’ are accepted and
     expanded.  Directories are recursively traversed and all files are
     added to the archive.

     If ROOTDIR is defined then any files without absolute pathnames are
     located relative to ROOTDIR rather than the current directory.

     The optional output FILELIST is a list of the files that were
     included in the archive.

     See also: *note untar: XREFuntar, *note unpack: XREFunpack, *note
     bzip2: XREFbzip2, *note gzip: XREFgzip, *note zip: XREFzip.

 -- : untar (TARFILE)
 -- : untar (TARFILE, DIR)
 -- : FILELIST = untar (...)
     Unpack the TAR archive TARFILE.

     If DIR is specified the files are unpacked in this directory rather
     than the one where TARFILE is located.

     The optional output FILELIST is a list of the uncompressed files.

     See also: *note tar: XREFtar, *note unpack: XREFunpack, *note
     bunzip2: XREFbunzip2, *note gunzip: XREFgunzip, *note unzip:
     XREFunzip.

 -- : FILELIST = zip (ZIPFILE, FILES)
 -- : FILELIST = zip (ZIPFILE, FILES, ROOTDIR)
     Compress the list of files and directories specified in FILES into
     the ZIP archive ZIPFILE.

     FILES is a character array or cell array of strings.  Shell
     wildcards in the filename such as ‘*’ or ‘?’ are accepted and
     expanded.  Directories are recursively traversed and all files are
     compressed and added to the archive.

     If ROOTDIR is defined then any files without absolute pathnames are
     located relative to ROOTDIR rather than the current directory.

     The optional output FILELIST is a list of the files that were
     included in the archive.

     See also: *note unzip: XREFunzip, *note unpack: XREFunpack, *note
     bzip2: XREFbzip2, *note gzip: XREFgzip, *note tar: XREFtar.

 -- : unzip (ZIPFILE)
 -- : unzip (ZIPFILE, DIR)
 -- : FILELIST = unzip (...)
     Unpack the ZIP archive ZIPFILE.

     If DIR is specified the files are unpacked in this directory rather
     than the one where ZIPFILE is located.

     The optional output FILELIST is a list of the uncompressed files.

     See also: *note zip: XREFzip, *note unpack: XREFunpack, *note
     bunzip2: XREFbunzip2, *note gunzip: XREFgunzip, *note untar:
     XREFuntar.

 -- : FILES = unpack (FILE)
 -- : FILES = unpack (FILE, DIR)
 -- : FILES = unpack (FILE, DIR, FILETYPE)
     Unpack the archive FILE based on its extension to the directory
     DIR.

     If FILE is a list of strings, then each file is unpacked
     individually.  Shell wildcards in the filename such as ‘*’ or ‘?’
     are accepted and expanded.

     If DIR is not specified or is empty (‘[]’), it defaults to the
     current directory.  If a directory is in the file list, then
     FILETYPE must also be specified.

     The specific archive filetype is inferred from the extension of the
     file.  The FILETYPE may also be specified directly using a string
     which corresponds to a known extension.

     Valid filetype extensions:

     ‘bz’
     ‘bz2’
          bzip archive

     ‘gz’
          gzip archive

     ‘tar’
          tar archive

     ‘tarbz’
     ‘tarbz2’
     ‘tbz’
     ‘tbz2’
          tar + bzip archive

     ‘targz’
     ‘tgz’
          tar + gzip archive

     ‘z’
          compress archive

     ‘zip’
          zip archive

     The optional return value is a list of FILES unpacked.

     See also: *note bunzip2: XREFbunzip2, *note gunzip: XREFgunzip,
     *note unzip: XREFunzip, *note untar: XREFuntar, *note bzip2:
     XREFbzip2, *note gzip: XREFgzip, *note zip: XREFzip, *note tar:
     XREFtar.

 -- : FILELIST = bzip2 (FILES)
 -- : FILELIST = bzip2 (FILES, DIR)
     Compress the list of files specified in FILES.

     FILES is a character array or cell array of strings.  Shell
     wildcards in the filename such as ‘*’ or ‘?’ are accepted and
     expanded.  Each file is compressed separately and a new file with a
     ‘".bz2"’ extension is created.  The original files are not
     modified, but existing compressed files will be silently
     overwritten.

     If DIR is defined the compressed files are placed in this
     directory, rather than the original directory where the
     uncompressed file resides.  Note that this does not replicate a
     directory tree in DIR which may lead to files overwriting each
     other if there are multiple files with the same name.

     If DIR does not exist it is created.

     The optional output FILELIST is a list of the compressed files.

     See also: *note bunzip2: XREFbunzip2, *note unpack: XREFunpack,
     *note gzip: XREFgzip, *note zip: XREFzip, *note tar: XREFtar.


File: octave.info,  Node: Networking Utilities,  Next: Controlling Subprocesses,  Prev: File Archiving Utilities,  Up: System Utilities

36.4 Networking Utilities
=========================

* Menu:

* FTP Objects::
* URL Manipulation::
* Base64 and Binary Data Transmission::

 -- : gethostname ()
     Return the hostname of the system where Octave is running.


File: octave.info,  Node: FTP Objects,  Next: URL Manipulation,  Up: Networking Utilities

36.4.1 FTP Objects
------------------

Octave supports the FTP protocol through an object-oriented interface.
Use the function ‘ftp’ to create an FTP object which represents the
connection.  All FTP functions take an FTP object as the first argument.

 -- : F = ftp (HOST)
 -- : F = ftp (HOST, USERNAME, PASSWORD)
     Connect to the FTP server HOST with USERNAME and PASSWORD.

     If USERNAME and PASSWORD are not specified, user "anonymous" with
     no password is used.  The returned FTP object F represents the
     established FTP connection.

     The list of actions for an FTP object are shown below.  All
     functions require an FTP object as the first argument.

     Method      Description
     -----------------------------------------------------------------------
     ascii       Set transfer type to ascii
     binary      Set transfer type to binary
     cd          Change remote working directory
     close       Close FTP connection
     delete      Delete remote file
     dir         List remote directory contents
     mget        Download remote files
     mkdir       Create remote directory
     mput        Upload local files
     rename      Rename remote file or directory
     rmdir       Remove remote directory

 -- : close (F)
     Close the FTP connection represented by the FTP object F.

     F is an FTP object returned by the ‘ftp’ function.

 -- : mget (F, FILE)
 -- : mget (F, DIR)
 -- : mget (F, REMOTE_NAME, TARGET)
     Download a remote file FILE or directory DIR to the local directory
     on the FTP connection F.

     F is an FTP object returned by the ‘ftp’ function.

     The arguments FILE and DIR can include wildcards and any files or
     directories on the remote server that match will be downloaded.

     If a third string argument TARGET is given, then it must indicate
     the path to the local destination directory.  TARGET may be a
     relative or absolute path.

 -- : mput (F, FILE)
     Upload the local file FILE into the current remote directory on the
     FTP connection F.

     F is an FTP object returned by the ftp function.

     The argument FILE is passed through the ‘glob’ function and any
     files that match the wildcards in FILE will be uploaded.

 -- : cd (F)
 -- : cd (F, PATH)
     Get or set the remote directory on the FTP connection F.

     F is an FTP object returned by the ‘ftp’ function.

     If PATH is not specified, return the remote current working
     directory.  Otherwise, set the remote directory to PATH and return
     the new remote working directory.

     If the directory does not exist, an error message is printed and
     the working directory is not changed.

 -- : LST = dir (F)
     List the current directory in verbose form for the FTP connection
     F.

     F is an FTP object returned by the ‘ftp’ function.

 -- : ascii (F)
     Set the FTP connection F to use ASCII mode for transfers.

     ASCII mode is only appropriate for text files as it will convert
     the remote host’s newline representation to the local host’s
     newline representation.

     F is an FTP object returned by the ‘ftp’ function.

 -- : binary (F)
     Set the FTP connection F to use binary mode for transfers.

     In binary mode there is no conversion of newlines from the remote
     representation to the local representation.

     F is an FTP object returned by the ‘ftp’ function.

 -- : delete (F, FILE)
     Delete the remote file FILE over the FTP connection F.

     F is an FTP object returned by the ‘ftp’ function.

 -- : rename (F, OLDNAME, NEWNAME)
     Rename or move the remote file or directory OLDNAME to NEWNAME,
     over the FTP connection F.

     F is an FTP object returned by the ftp function.

 -- : mkdir (F, PATH)
     Create the remote directory PATH, over the FTP connection F.

     F is an FTP object returned by the ‘ftp’ function.

 -- : rmdir (F, PATH)
     Remove the remote directory PATH, over the FTP connection F.

     F is an FTP object returned by the ‘ftp’ function.


File: octave.info,  Node: URL Manipulation,  Next: Base64 and Binary Data Transmission,  Prev: FTP Objects,  Up: Networking Utilities

36.4.2 URL Manipulation
-----------------------

 -- : S = urlread (URL)
 -- : [S, SUCCESS] = urlread (URL)
 -- : [S, SUCCESS, MESSAGE] = urlread (URL)
 -- : [...] = urlread (URL, METHOD, PARAM)
     Download a remote file specified by its URL and return its content
     in string S.

     For example:

          s = urlread ("ftp://ftp.octave.org/pub/README");

     The variable SUCCESS is 1 if the download was successful, otherwise
     it is 0 in which case MESSAGE contains an error message.

     If no output argument is specified and an error occurs, then the
     error is signaled through Octave’s error handling mechanism.

     This function uses libcurl.  Curl supports, among others, the HTTP,
     FTP, and FILE protocols.  Username and password may be specified in
     the URL.  For example:

          s = urlread ("http://user:password@example.com/file.txt");

     GET and POST requests can be specified by METHOD and PARAM.  The
     parameter METHOD is either ‘get’ or ‘post’ and PARAM is a cell
     array of parameter and value pairs.  For example:

          s = urlread ("http://www.google.com/search", "get",
                      {"query", "octave"});

     See also: *note urlwrite: XREFurlwrite.

 -- : urlwrite (URL, LOCALFILE)
 -- : F = urlwrite (URL, LOCALFILE)
 -- : [F, SUCCESS] = urlwrite (URL, LOCALFILE)
 -- : [F, SUCCESS, MESSAGE] = urlwrite (URL, LOCALFILE)
     Download a remote file specified by its URL and save it as
     LOCALFILE.

     For example:

          urlwrite ("ftp://ftp.octave.org/pub/README",
                    "README.txt");

     The full path of the downloaded file is returned in F.

     The variable SUCCESS is 1 if the download was successful, otherwise
     it is 0 in which case MESSAGE contains an error message.

     If no output argument is specified and an error occurs, then the
     error is signaled through Octave’s error handling mechanism.

     This function uses libcurl.  Curl supports, among others, the HTTP,
     FTP, and FILE protocols.  Username and password may be specified in
     the URL, for example:

          urlwrite ("http://username:password@example.com/file.txt",
                    "file.txt");

     GET and POST requests can be specified by METHOD and PARAM.  The
     parameter METHOD is either ‘get’ or ‘post’ and PARAM is a cell
     array of parameter and value pairs.  For example:

          urlwrite ("http://www.google.com/search", "search.html",
                    "get", {"query", "octave"});

     See also: *note urlread: XREFurlread.


File: octave.info,  Node: Base64 and Binary Data Transmission,  Prev: URL Manipulation,  Up: Networking Utilities

36.4.3 Base64 and Binary Data Transmission
------------------------------------------

Some transmission channels can not accept binary data.  It is customary
to encode binary data in Base64 for transmission and to decode the data
upon reception.

 -- : S = base64_encode (X)
     Encode a double matrix or array X into the base64 format string S.

     See also: *note base64_decode: XREFbase64_decode.

 -- : X = base64_decode (S)
 -- : X = base64_decode (S, DIMS)
     Decode the double matrix or array X from the base64 encoded string
     S.

     The optional input parameter DIMS should be a vector containing the
     dimensions of the decoded array.

     See also: *note base64_encode: XREFbase64_encode.


File: octave.info,  Node: Controlling Subprocesses,  Next: Process ID Information,  Prev: Networking Utilities,  Up: System Utilities

36.5 Controlling Subprocesses
=============================

Octave includes some high-level commands like ‘system’ and ‘popen’ for
starting subprocesses.  If you want to run another program to perform
some task and then look at its output, you will probably want to use
these functions.

   Octave also provides several very low-level Unix-like functions which
can also be used for starting subprocesses, but you should probably only
use them if you can’t find any way to do what you need with the
higher-level functions.

 -- : system ("STRING")
 -- : system ("STRING", RETURN_OUTPUT)
 -- : system ("STRING", RETURN_OUTPUT, TYPE)
 -- : [STATUS, OUTPUT] = system (...)
     Execute a shell command specified by STRING.

     If the optional argument TYPE is "async", the process is started in
     the background and the process ID of the child process is returned
     immediately.  Otherwise, the child process is started and Octave
     waits until it exits.  If the TYPE argument is omitted, it defaults
     to the value "sync".

     If SYSTEM is called with one or more output arguments, or if the
     optional argument RETURN_OUTPUT is true and the subprocess is
     started synchronously, then the output from the command is returned
     as a variable.  Otherwise, if the subprocess is executed
     synchronously, its output is sent to the standard output.  To send
     the output of a command executed with ‘system’ through the pager,
     use a command like

          [~, text] = system ("cmd");
          more on;
          disp (text);

     or

          more on;
          printf ("%s\n", nthargout (2, "system", "cmd"));

     The ‘system’ function can return two values.  The first is the exit
     status of the command and the second is any output from the command
     that was written to the standard output stream.  For example,

          [status, output] = system ("echo foo & exit 2");

     will set the variable OUTPUT to the string ‘foo’, and the variable
     STATUS to the integer ‘2’.

     For commands run asynchronously, STATUS is the process id of the
     command shell that is started to run the command.

     The shell used for executing commands varies with operating system
     and is typically ‘/bin/sh’ for UNIX systems and ‘cmd.exe’ for
     Windows systems.

     See also: *note unix: XREFunix, *note dos: XREFdos.

 -- : unix ("COMMAND")
 -- : STATUS = unix ("COMMAND")
 -- : [STATUS, TEXT] = unix ("COMMAND")
 -- : [...] = unix ("COMMAND", "-echo")
     Execute a system command if running under a Unix-like operating
     system, otherwise do nothing.

     Octave waits for the external command to finish before returning
     the exit status of the program in STATUS and any output in TEXT.

     When called with no output argument, or the "-echo" argument is
     given, then TEXT is also sent to standard output.

     See also: *note dos: XREFdos, *note system: XREFsystem, *note
     isunix: XREFisunix, *note ismac: XREFismac, *note ispc: XREFispc.

 -- : dos ("COMMAND")
 -- : STATUS = dos ("COMMAND")
 -- : [STATUS, TEXT] = dos ("COMMAND")
 -- : [...] = dos ("COMMAND", "-echo")
     Execute a system command if running under a Windows-like operating
     system, otherwise do nothing.

     Octave waits for the external command to finish before returning
     the exit status of the program in STATUS and any output in TEXT.

     When called with no output argument, or the "-echo" argument is
     given, then TEXT is also sent to standard output.

     See also: *note unix: XREFunix, *note system: XREFsystem, *note
     isunix: XREFisunix, *note ismac: XREFismac, *note ispc: XREFispc.

 -- : open FILE
 -- : OUTPUT = open (FILE)
     Open the file FILE in Octave or in an external application based on
     the file type as determined by the filename extension.

     By default, recognized file types are

     ‘.m’
          Open file in the editor.  No OUTPUT value is returned.

     ‘.mat’
     ‘octave-workspace’
          Open the data file with ‘load’.  If no return value OUTPUT is
          requested, variables are loaded in the base workspace.
          Otherwise OUTPUT will be a structure containing loaded data.
          *Note load function: XREFload.

     ‘.ofig’
          Open the figure with hgload.  *Note hgload function:
          XREFhgload.

     ‘.fig, .ofig’
          Load the figure

     ‘.exe’
          Execute the program (on Windows systems only).  No OUTPUT
          value is returned.

     Custom file extensions may also be handled if a function ‘openxxx’,
     where ‘xxx’ is the extension, is found in the load path.  The
     function must accept the file name as input.  For example, in order
     to load ".dat" data files in the base workspace, as is done by
     default for ".mat" files, one may define "opendat.m" with the
     following contents:

          function retval = opendat (fname)
            evalin ("base", sprintf ("load ('%s');", fname));
          endfunction

     Other file types are opened in the appropriate external
     application.

 -- : OUTPUT = perl (SCRIPTFILE)
 -- : OUTPUT = perl (SCRIPTFILE, ARGUMENT1, ARGUMENT2, ...)
 -- : [OUTPUT, STATUS] = perl (...)
     Invoke Perl script SCRIPTFILE, possibly with a list of command line
     arguments.

     Return output in OUTPUT and optional status in STATUS.  If
     SCRIPTFILE is not an absolute filename it is searched for in the
     current directory and then in the Octave loadpath.

     See also: *note system: XREFsystem, *note python: XREFpython.

 -- : OUTPUT = python (SCRIPTFILE)
 -- : OUTPUT = python (SCRIPTFILE, ARGUMENT1, ARGUMENT2, ...)
 -- : [OUTPUT, STATUS] = python (...)
     Invoke Python script SCRIPTFILE, possibly with a list of command
     line arguments.

     Return output in OUTPUT and optional status in STATUS.  If
     SCRIPTFILE is not an absolute filename it is searched for in the
     current directory and then in the Octave loadpath.

     See also: *note system: XREFsystem, *note perl: XREFperl.

 -- : FID = popen (COMMAND, MODE)
     Start a process and create a pipe.

     The name of the command to run is given by COMMAND.  The argument
     MODE may be

     "r"
          The pipe will be connected to the standard output of the
          process, and open for reading.

     "w"
          The pipe will be connected to the standard input of the
          process, and open for writing.

     The file identifier corresponding to the input or output stream of
     the process is returned in FID.

     For example:

          fid = popen ("ls -ltr / | tail -3", "r");
          while (ischar (s = fgets (fid)))
            fputs (stdout, s);
          endwhile

             ⊣ drwxr-xr-x  33 root  root  3072 Feb 15 13:28 etc
             ⊣ drwxr-xr-x   3 root  root  1024 Feb 15 13:28 lib
             ⊣ drwxrwxrwt  15 root  root  2048 Feb 17 14:53 tmp

     See also: *note popen2: XREFpopen2.

 -- : pclose (FID)
     Close a file identifier that was opened by ‘popen’.

     The function ‘fclose’ may also be used for the same purpose.

     See also: *note fclose: XREFfclose, *note popen: XREFpopen.

 -- : [IN, OUT, PID] = popen2 (COMMAND, ARGS)
     Start a subprocess with two-way communication.

     The name of the process is given by COMMAND, and ARGS is an array
     or cell array of strings containing options for the command.

     The file identifiers for the input and output streams of the
     subprocess are returned in IN and OUT.  If execution of the command
     is successful, PID contains the process ID of the subprocess.
     Otherwise, PID is −1.

     For example:

          [in, out, pid] = popen2 ("sort", "-r");
          fputs (in, "these\nare\nsome\nstrings\n");
          fclose (in);
          EAGAIN = errno ("EAGAIN");
          done = false;
          do
            s = fgets (out);
            if (ischar (s))
              fputs (stdout, s);
            elseif (errno () == EAGAIN)
              pause (0.1);
              fclear (out);
            else
              done = true;
            endif
          until (done)
          fclose (out);
          waitpid (pid);

             ⊣ these
             ⊣ strings
             ⊣ some
             ⊣ are

     Note that ‘popen2’, unlike ‘popen’, will not "reap" the child
     process.  If you don’t use ‘waitpid’ to check the child’s exit
     status, it will linger until Octave exits.

     See also: *note popen: XREFpopen, *note waitpid: XREFwaitpid.

 -- : VAL = EXEC_PATH ()
 -- : OLD_VAL = EXEC_PATH (NEW_VAL)
 -- : EXEC_PATH (NEW_VAL, "local")
     Query or set the internal variable that specifies a colon separated
     list of directories to append to the shell PATH when executing
     external programs.

     The initial value of is taken from the environment variable
     ‘OCTAVE_EXEC_PATH’, but that value can be overridden by the command
     line argument ‘--exec-path PATH’.

     When called from inside a function with the "local" option, the
     variable is changed locally for the function and any subroutines it
     calls.  The original variable value is restored when exiting the
     function.

     See also: *note IMAGE_PATH: XREFIMAGE_PATH, *note OCTAVE_HOME:
     XREFOCTAVE_HOME, *note OCTAVE_EXEC_HOME: XREFOCTAVE_EXEC_HOME.

   In most cases, the following functions simply decode their arguments
and make the corresponding Unix system calls.  For a complete example of
how they can be used, look at the definition of the function ‘popen2’.

 -- : [PID, MSG] = fork ()
     Create a copy of the current process.

     Fork can return one of the following values:

     > 0
          You are in the parent process.  The value returned from ‘fork’
          is the process id of the child process.  You should probably
          arrange to wait for any child processes to exit.

     0
          You are in the child process.  You can call ‘exec’ to start
          another process.  If that fails, you should probably call
          ‘exit’.

     < 0
          The call to ‘fork’ failed for some reason.  You must take
          evasive action.  A system dependent error message will be
          waiting in MSG.

 -- : [ERR, MSG] = exec (FILE, ARGS)
     Replace current process with a new process.

     Calling ‘exec’ without first calling ‘fork’ will terminate your
     current Octave process and replace it with the program named by
     FILE.  For example,

          exec ("ls", "-l")

     will run ‘ls’ and return you to your shell prompt.

     If successful, ‘exec’ does not return.  If ‘exec’ does return, ERR
     will be nonzero, and MSG will contain a system-dependent error
     message.

 -- : [READ_FD, WRITE_FD, ERR, MSG] = pipe ()
     Create a pipe and return the reading and writing ends of the pipe
     into READ_FD and WRITE_FD respectively.

     If successful, ERR is 0 and MSG is an empty string.  Otherwise, ERR
     is nonzero and MSG contains a system-dependent error message.

     See also: *note mkfifo: XREFmkfifo.

 -- : [FID, MSG] = dup2 (OLD, NEW)
     Duplicate a file descriptor.

     If successful, FID is greater than zero and contains the new file
     ID.  Otherwise, FID is negative and MSG contains a system-dependent
     error message.

     See also: *note fopen: XREFfopen, *note fclose: XREFfclose, *note
     fcntl: XREFfcntl.

 -- : [PID, STATUS, MSG] = waitpid (PID, OPTIONS)
     Wait for process PID to terminate.

     The PID argument can be:

     −1
          Wait for any child process.

     0
          Wait for any child process whose process group ID is equal to
          that of the Octave interpreter process.

     > 0
          Wait for termination of the child process with ID PID.

     The OPTIONS argument can be a bitwise OR of zero or more of the
     following constants:

     ‘0’
          Wait until signal is received or a child process exits (this
          is the default if the OPTIONS argument is missing).

     ‘WNOHANG’
          Do not hang if status is not immediately available.

     ‘WUNTRACED’
          Report the status of any child processes that are stopped, and
          whose status has not yet been reported since they stopped.

     ‘WCONTINUE’
          Return if a stopped child has been resumed by delivery of
          ‘SIGCONT’.  This value may not be meaningful on all systems.

     If the returned value of PID is greater than 0, it is the process
     ID of the child process that exited.  If an error occurs, PID will
     be less than zero and MSG will contain a system-dependent error
     message.  The value of STATUS contains additional system-dependent
     information about the subprocess that exited.

     See also: *note WCONTINUE: XREFWCONTINUE, *note WCOREDUMP:
     XREFWCOREDUMP, *note WEXITSTATUS: XREFWEXITSTATUS, *note
     WIFCONTINUED: XREFWIFCONTINUED, *note WIFSIGNALED: XREFWIFSIGNALED,
     *note WIFSTOPPED: XREFWIFSTOPPED, *note WNOHANG: XREFWNOHANG, *note
     WSTOPSIG: XREFWSTOPSIG, *note WTERMSIG: XREFWTERMSIG, *note
     WUNTRACED: XREFWUNTRACED.

 -- : WCONTINUE ()
     Return the numerical value of the ‘WCONTINUE’ macro.

     ‘WCONTINUE’ is the option argument that may be passed to ‘waitpid’
     to indicate that it should also return if a stopped child has been
     resumed by delivery of a ‘SIGCONT’ signal.

     See also: *note waitpid: XREFwaitpid, *note WNOHANG: XREFWNOHANG,
     *note WUNTRACED: XREFWUNTRACED.

 -- : WCOREDUMP (STATUS)
     Given STATUS from a call to ‘waitpid’, return true if the child
     produced a core dump.

     This function should only be employed if ‘WIFSIGNALED’ returned
     true.  The macro used to implement this function is not specified
     in POSIX.1-2001 and is not available on some Unix implementations
     (e.g., AIX, SunOS).

     See also: *note waitpid: XREFwaitpid, *note WIFEXITED:
     XREFWIFEXITED, *note WEXITSTATUS: XREFWEXITSTATUS, *note
     WIFSIGNALED: XREFWIFSIGNALED, *note WTERMSIG: XREFWTERMSIG, *note
     WIFSTOPPED: XREFWIFSTOPPED, *note WSTOPSIG: XREFWSTOPSIG, *note
     WIFCONTINUED: XREFWIFCONTINUED.

 -- : WEXITSTATUS (STATUS)
     Given STATUS from a call to ‘waitpid’, return the exit status of
     the child.

     This function should only be employed if ‘WIFEXITED’ returned true.

     See also: *note waitpid: XREFwaitpid, *note WIFEXITED:
     XREFWIFEXITED, *note WIFSIGNALED: XREFWIFSIGNALED, *note WTERMSIG:
     XREFWTERMSIG, *note WCOREDUMP: XREFWCOREDUMP, *note WIFSTOPPED:
     XREFWIFSTOPPED, *note WSTOPSIG: XREFWSTOPSIG, *note WIFCONTINUED:
     XREFWIFCONTINUED.

 -- : WIFCONTINUED (STATUS)
     Given STATUS from a call to ‘waitpid’, return true if the child
     process was resumed by delivery of ‘SIGCONT’.

     See also: *note waitpid: XREFwaitpid, *note WIFEXITED:
     XREFWIFEXITED, *note WEXITSTATUS: XREFWEXITSTATUS, *note
     WIFSIGNALED: XREFWIFSIGNALED, *note WTERMSIG: XREFWTERMSIG, *note
     WCOREDUMP: XREFWCOREDUMP, *note WIFSTOPPED: XREFWIFSTOPPED, *note
     WSTOPSIG: XREFWSTOPSIG.

 -- : WIFSIGNALED (STATUS)
     Given STATUS from a call to ‘waitpid’, return true if the child
     process was terminated by a signal.

     See also: *note waitpid: XREFwaitpid, *note WIFEXITED:
     XREFWIFEXITED, *note WEXITSTATUS: XREFWEXITSTATUS, *note WTERMSIG:
     XREFWTERMSIG, *note WCOREDUMP: XREFWCOREDUMP, *note WIFSTOPPED:
     XREFWIFSTOPPED, *note WSTOPSIG: XREFWSTOPSIG, *note WIFCONTINUED:
     XREFWIFCONTINUED.

 -- : WIFSTOPPED (STATUS)
     Given STATUS from a call to ‘waitpid’, return true if the child
     process was stopped by delivery of a signal.

     This is only possible if the call was done using ‘WUNTRACED’ or
     when the child is being traced (see ptrace(2)).

     See also: *note waitpid: XREFwaitpid, *note WIFEXITED:
     XREFWIFEXITED, *note WEXITSTATUS: XREFWEXITSTATUS, *note
     WIFSIGNALED: XREFWIFSIGNALED, *note WTERMSIG: XREFWTERMSIG, *note
     WCOREDUMP: XREFWCOREDUMP, *note WSTOPSIG: XREFWSTOPSIG, *note
     WIFCONTINUED: XREFWIFCONTINUED.

 -- : WIFEXITED (STATUS)
     Given STATUS from a call to ‘waitpid’, return true if the child
     terminated normally.

     See also: *note waitpid: XREFwaitpid, *note WEXITSTATUS:
     XREFWEXITSTATUS, *note WIFSIGNALED: XREFWIFSIGNALED, *note
     WTERMSIG: XREFWTERMSIG, *note WCOREDUMP: XREFWCOREDUMP, *note
     WIFSTOPPED: XREFWIFSTOPPED, *note WSTOPSIG: XREFWSTOPSIG, *note
     WIFCONTINUED: XREFWIFCONTINUED.

 -- : WNOHANG ()
     Return the numerical value of the ‘WNOHANG’ macro.

     ‘WNOHANG’ is the option argument that may be passed to ‘waitpid’ to
     indicate that it should return its status immediately instead of
     waiting for a process to exit.

     See also: *note waitpid: XREFwaitpid, *note WUNTRACED:
     XREFWUNTRACED, *note WCONTINUE: XREFWCONTINUE.

 -- : WSTOPSIG (STATUS)
     Given STATUS from a call to ‘waitpid’, return the number of the
     signal which caused the child to stop.

     This function should only be employed if ‘WIFSTOPPED’ returned
     true.

     See also: *note waitpid: XREFwaitpid, *note WIFEXITED:
     XREFWIFEXITED, *note WEXITSTATUS: XREFWEXITSTATUS, *note
     WIFSIGNALED: XREFWIFSIGNALED, *note WTERMSIG: XREFWTERMSIG, *note
     WCOREDUMP: XREFWCOREDUMP, *note WIFSTOPPED: XREFWIFSTOPPED, *note
     WIFCONTINUED: XREFWIFCONTINUED.

 -- : WTERMSIG (STATUS)
     Given STATUS from a call to ‘waitpid’, return the number of the
     signal that caused the child process to terminate.

     This function should only be employed if ‘WIFSIGNALED’ returned
     true.

     See also: *note waitpid: XREFwaitpid, *note WIFEXITED:
     XREFWIFEXITED, *note WEXITSTATUS: XREFWEXITSTATUS, *note
     WIFSIGNALED: XREFWIFSIGNALED, *note WCOREDUMP: XREFWCOREDUMP, *note
     WIFSTOPPED: XREFWIFSTOPPED, *note WSTOPSIG: XREFWSTOPSIG, *note
     WIFCONTINUED: XREFWIFCONTINUED.

 -- : WUNTRACED ()
     Return the numerical value of the ‘WUNTRACED’ macro.

     ‘WUNTRACED’ is the option argument that may be passed to ‘waitpid’
     to indicate that it should also return if the child process has
     stopped but is not traced via the ‘ptrace’ system call

     See also: *note waitpid: XREFwaitpid, *note WNOHANG: XREFWNOHANG,
     *note WCONTINUE: XREFWCONTINUE.

 -- : [ERR, MSG] = fcntl (FID, REQUEST, ARG)
     Change the properties of the open file FID.

     The following values may be passed as REQUEST:

     ‘F_DUPFD’
          Return a duplicate file descriptor.

     ‘F_GETFD’
          Return the file descriptor flags for FID.

     ‘F_SETFD’
          Set the file descriptor flags for FID.

     ‘F_GETFL’
          Return the file status flags for FID.  The following codes may
          be returned (some of the flags may be undefined on some
          systems).

          ‘O_RDONLY’
               Open for reading only.

          ‘O_WRONLY’
               Open for writing only.

          ‘O_RDWR’
               Open for reading and writing.

          ‘O_APPEND’
               Append on each write.

          ‘O_CREAT’
               Create the file if it does not exist.

          ‘O_NONBLOCK’
               Non-blocking mode.

          ‘O_SYNC’
               Wait for writes to complete.

          ‘O_ASYNC’
               Asynchronous I/O.

     ‘F_SETFL’
          Set the file status flags for FID to the value specified by
          ARG.  The only flags that can be changed are ‘O_APPEND’ and
          ‘O_NONBLOCK’.

     If successful, ERR is 0 and MSG is an empty string.  Otherwise, ERR
     is nonzero and MSG contains a system-dependent error message.

     See also: *note fopen: XREFfopen, *note dup2: XREFdup2.

 -- : [ERR, MSG] = kill (PID, SIG)
     Send signal SIG to process PID.

     If PID is positive, then signal SIG is sent to PID.

     If PID is 0, then signal SIG is sent to every process in the
     process group of the current process.

     If PID is -1, then signal SIG is sent to every process except
     process 1.

     If PID is less than -1, then signal SIG is sent to every process in
     the process group -PID.

     If SIG is 0, then no signal is sent, but error checking is still
     performed.

     Return 0 if successful, otherwise return -1.

 -- : SIG ()
     Return a structure containing Unix signal names and their defined
     values.


File: octave.info,  Node: Process ID Information,  Next: Environment Variables,  Prev: Controlling Subprocesses,  Up: System Utilities

36.6 Process, Group, and User IDs
=================================

 -- : pgid = getpgrp ()
     Return the process group id of the current process.

 -- : pid = getpid ()
     Return the process id of the current process.

     See also: *note getppid: XREFgetppid.

 -- : pid = getppid ()
     Return the process id of the parent process.

     See also: *note getpid: XREFgetpid.

 -- : euid = geteuid ()
     Return the effective user id of the current process.

     See also: *note getuid: XREFgetuid.

 -- : uid = getuid ()
     Return the real user id of the current process.

     See also: *note geteuid: XREFgeteuid.

 -- : egid = getegid ()
     Return the effective group id of the current process.

     See also: *note getgid: XREFgetgid.

 -- : gid = getgid ()
     Return the real group id of the current process.

     See also: *note getegid: XREFgetegid.


File: octave.info,  Node: Environment Variables,  Next: Current Working Directory,  Prev: Process ID Information,  Up: System Utilities

36.7 Environment Variables
==========================

 -- : getenv (VAR)
     Return the value of the environment variable VAR.

     For example,

          getenv ("PATH")

     returns a string containing the value of your path.

     See also: *note setenv: XREFsetenv, *note unsetenv: XREFunsetenv.

 -- : setenv (VAR, VALUE)
 -- : setenv (VAR)
 -- : putenv (...)
     Set the value of the environment variable VAR to VALUE.

     If no VALUE is specified then the variable will be assigned the
     null string.

     See also: *note unsetenv: XREFunsetenv, *note getenv: XREFgetenv.

 -- : STATUS = unsetenv (VAR)
     Delete the environment variable VAR.

     Return 0 if the variable was deleted, or did not exist, and -1 if
     an error occurred.

     See also: *note setenv: XREFsetenv, *note getenv: XREFgetenv.

 -- : HOMEDIR = get_home_directory ()
     Return the current home directory.

     On most systems, this is equivalent to ‘getenv ("HOME")’.  On
     Windows systems, if the environment variable ‘HOME’ is not set then
     it is equivalent to ‘fullfile (getenv ("HOMEDRIVE"), getenv
     ("HOMEPATH"))’

     See also: *note getenv: XREFgetenv.


File: octave.info,  Node: Current Working Directory,  Next: Password Database Functions,  Prev: Environment Variables,  Up: System Utilities

36.8 Current Working Directory
==============================

 -- : cd DIR
 -- : cd
 -- : OLD_DIR = cd (DIR)
 -- : chdir ...
     Change the current working directory to DIR.

     If DIR is omitted, the current directory is changed to the user’s
     home directory ("~").

     For example,

          cd ~/octave

     changes the current working directory to ‘~/octave’.  If the
     directory does not exist, an error message is printed and the
     working directory is not changed.

     ‘chdir’ is an alias for ‘cd’ and can be used in all of the same
     calling formats.

     Compatibility Note: When called with no arguments, MATLAB prints
     the present working directory rather than changing to the user’s
     home directory.

     See also: *note pwd: XREFpwd, *note mkdir: XREFmkdir, *note rmdir:
     XREFrmdir, *note dir: XREFdir, *note ls: XREFls.

 -- : ls
 -- : ls FILENAMES
 -- : ls OPTIONS
 -- : ls OPTIONS FILENAMES
 -- : LIST = ls (...)

     List directory contents.

     The ‘ls’ command is implemented by calling the native operating
     system’s directory listing command—available OPTIONS will vary from
     system to system.

     Filenames are subject to shell expansion if they contain any
     wildcard characters ‘*’, ‘?’, ‘[]’.  To find a literal example of a
     wildcard character the wildcard must be escaped using the backslash
     operator ‘\’.

     If the optional output LIST is requested then ‘ls’ returns a
     character array with one row for each file/directory name.

     Example usage on a UNIX-like system:

          ls -l
               ⊣ total 12
               ⊣ -rw-r--r--   1 jwe  users  4488 Aug 19 04:02 foo.m
               ⊣ -rw-r--r--   1 jwe  users  1315 Aug 17 23:14 bar.m

     See also: *note dir: XREFdir, *note readdir: XREFreaddir, *note
     glob: XREFglob, *note what: XREFwhat, *note stat: XREFstat, *note
     filesep: XREFfilesep, *note ls_command: XREFls_command.

 -- : VAL = ls_command ()
 -- : OLD_VAL = ls_command (NEW_VAL)
     Query or set the shell command used by Octave’s ‘ls’ command.

     See also: *note ls: XREFls.

 -- : dir
 -- : dir (DIRECTORY)
 -- : [LIST] = dir (DIRECTORY)
     Display file listing for directory DIRECTORY.

     If DIRECTORY is not specified then list the present working
     directory.

     If a return value is requested, return a structure array with the
     fields

     name
          File or directory name.

     folder
          Location of file or directory

     date
          Timestamp of file modification (string value).

     bytes
          File size in bytes.

     isdir
          True if name is a directory.

     datenum
          Timestamp of file modification as serial date number (double).

     statinfo
          Information structure returned from ‘stat’.

     If DIRECTORY is a filename, rather than a directory, then return
     information about the named file.  DIRECTORY may also be a list
     rather than a single directory or file.

     DIRECTORY is subject to shell expansion if it contains any wildcard
     characters ‘*’, ‘?’, ‘[]’.  To find a literal example of a wildcard
     character the wildcard must be escaped using the backslash operator
     ‘\’.

     Note that for symbolic links, ‘dir’ returns information about the
     file that the symbolic link points to rather than the link itself.
     However, if the link points to a nonexistent file, ‘dir’ returns
     information about the link.

     See also: *note ls: XREFls, *note readdir: XREFreaddir, *note glob:
     XREFglob, *note what: XREFwhat, *note stat: XREFstat, *note lstat:
     XREFlstat.

 -- : pwd ()
 -- : DIR = pwd ()
     Return the current working directory.

     See also: *note cd: XREFcd, *note dir: XREFdir, *note ls: XREFls,
     *note mkdir: XREFmkdir, *note rmdir: XREFrmdir.


File: octave.info,  Node: Password Database Functions,  Next: Group Database Functions,  Prev: Current Working Directory,  Up: System Utilities

36.9 Password Database Functions
================================

Octave’s password database functions return information in a structure
with the following fields.

‘name’
     The user name.

‘passwd’
     The encrypted password, if available.

‘uid’
     The numeric user id.

‘gid’
     The numeric group id.

‘gecos’
     The GECOS field.

‘dir’
     The home directory.

‘shell’
     The initial shell.

   In the descriptions of the following functions, this data structure
is referred to as a PW_STRUCT.

 -- : PW_STRUCT = getpwent ()
     Return a structure containing an entry from the password database,
     opening it if necessary.

     Once the end of the data has been reached, ‘getpwent’ returns 0.

     See also: *note setpwent: XREFsetpwent, *note endpwent:
     XREFendpwent.

 -- : PW_STRUCT = getpwuid (UID).
     Return a structure containing the first entry from the password
     database with the user ID UID.

     If the user ID does not exist in the database, ‘getpwuid’ returns
     0.

     See also: *note getpwnam: XREFgetpwnam.

 -- : PW_STRUCT = getpwnam (NAME)
     Return a structure containing the first entry from the password
     database with the user name NAME.

     If the user name does not exist in the database, ‘getpwname’
     returns 0.

     See also: *note getpwuid: XREFgetpwuid.

 -- : setpwent ()
     Return the internal pointer to the beginning of the password
     database.

     See also: *note getpwent: XREFgetpwent, *note endpwent:
     XREFendpwent.

 -- : endpwent ()
     Close the password database.

     See also: *note getpwent: XREFgetpwent, *note setpwent:
     XREFsetpwent.


File: octave.info,  Node: Group Database Functions,  Next: System Information,  Prev: Password Database Functions,  Up: System Utilities

36.10 Group Database Functions
==============================

Octave’s group database functions return information in a structure with
the following fields.

‘name’
     The user name.

‘passwd’
     The encrypted password, if available.

‘gid’
     The numeric group id.

‘mem’
     The members of the group.

   In the descriptions of the following functions, this data structure
is referred to as a GRP_STRUCT.

 -- : GRP_STRUCT = getgrent ()
     Return an entry from the group database, opening it if necessary.

     Once the end of data has been reached, ‘getgrent’ returns 0.

     See also: *note setgrent: XREFsetgrent, *note endgrent:
     XREFendgrent.

 -- : GRP_STRUCT = getgrgid (GID).
     Return the first entry from the group database with the group ID
     GID.

     If the group ID does not exist in the database, ‘getgrgid’ returns
     0.

     See also: *note getgrnam: XREFgetgrnam.

 -- : GRP_STRUCT = getgrnam (NAME)
     Return the first entry from the group database with the group name
     NAME.

     If the group name does not exist in the database, ‘getgrnam’
     returns 0.

     See also: *note getgrgid: XREFgetgrgid.

 -- : setgrent ()
     Return the internal pointer to the beginning of the group database.

     See also: *note getgrent: XREFgetgrent, *note endgrent:
     XREFendgrent.

 -- : endgrent ()
     Close the group database.

     See also: *note getgrent: XREFgetgrent, *note setgrent:
     XREFsetgrent.


File: octave.info,  Node: System Information,  Next: Hashing Functions,  Prev: Group Database Functions,  Up: System Utilities

36.11 System Information
========================

 -- : computer ()
 -- : C = computer ()
 -- : [C, MAXSIZE] = computer ()
 -- : [C, MAXSIZE, ENDIAN] = computer ()
 -- : ARCH = computer ("arch")
     Print or return a string of the form CPU-VENDOR-OS that identifies
     the type of computer that Octave is running on.

     If invoked with an output argument, the value is returned instead
     of printed.  For example:

          computer ()
             ⊣ x86_64-pc-linux-gnu

          mycomp = computer ()
             ⇒ mycomp = x86_64-pc-linux-gnu

     If two output arguments are requested, also return the maximum
     number of elements for an array.  This will depend on whether
     Octave has been compiled with 32-bit or 64-bit index vectors.

     If three output arguments are requested, also return the byte order
     of the current system as a character ("B" for big-endian or "L" for
     little-endian).

     If the argument "arch" is specified, return a string indicating the
     architecture of the computer on which Octave is running.

     See also: *note isunix: XREFisunix, *note ismac: XREFismac, *note
     ispc: XREFispc.

 -- : [UTS, ERR, MSG] = uname ()
     Return system information in the structure.

     For example:

          uname ()
             ⇒ {
                   sysname = x86_64
                   nodename = segfault
                   release = 2.6.15-1-amd64-k8-smp
                   version = Linux
                   machine = #2 SMP Thu Feb 23 04:57:49 UTC 2006
                }

     If successful, ERR is 0 and MSG is an empty string.  Otherwise, ERR
     is nonzero and MSG contains a system-dependent error message.

 -- : nproc ()
 -- : nproc (QUERY)
     Return the current number of available processors.

     If called with the optional argument QUERY, modify how processors
     are counted as follows:

     ‘all’
          total number of processors.

     ‘current’
          processors available to the current process.

     ‘overridable’
          same as ‘current’, but overridable through the
          ‘OMP_NUM_THREADS’ environment variable.

 -- : ispc ()
     Return true if Octave is running on a Windows system and false
     otherwise.

     See also: *note isunix: XREFisunix, *note ismac: XREFismac.

 -- : isunix ()
     Return true if Octave is running on a Unix-like system and false
     otherwise.

     See also: *note ismac: XREFismac, *note ispc: XREFispc.

 -- : ismac ()
     Return true if Octave is running on a Mac OS X system and false
     otherwise.

     See also: *note isunix: XREFisunix, *note ispc: XREFispc.

 -- : isieee ()
     Return true if your computer _claims_ to conform to the IEEE
     standard for floating point calculations.

     No actual tests are performed.

 -- : isdeployed ()
     Return true if the current program has been compiled and is running
     separately from the Octave interpreter and false if it is running
     in the Octave interpreter.

     Currently, this function always returns false in Octave.

 -- : isstudent ()
     Return true if running in the student edition of MATLAB.

     ‘isstudent’ always returns false in Octave.

     See also: *note false: XREFfalse.

 -- : OCTAVE_HOME ()
     Return the name of the top-level Octave installation directory.
     OCTAVE_HOME corresponds to the configuration variable PREFIX.

     See also: *note EXEC_PATH: XREFEXEC_PATH, *note IMAGE_PATH:
     XREFIMAGE_PATH, *note OCTAVE_EXEC_HOME: XREFOCTAVE_EXEC_HOME.

 -- : OCTAVE_EXEC_HOME ()
     Return the name of the top-level Octave installation directory for
     architecture-dependent files.  If not specified separately, the
     value is the same as OCTAVE_HOME.  OCTAVE_EXEC_HOME corresponds to
     the configuration variable EXEC_PREFIX.

     See also: *note EXEC_PATH: XREFEXEC_PATH, *note IMAGE_PATH:
     XREFIMAGE_PATH, *note OCTAVE_HOME: XREFOCTAVE_HOME.

 -- : matlabroot ()
     Return the name of the top-level Octave installation directory.

     This is an alias for the function ‘OCTAVE_HOME’ provided for
     compatibility.

     See also: *note OCTAVE_HOME: XREFOCTAVE_HOME.

 -- : OCTAVE_VERSION ()
     Return the version number of Octave as a string.

     See also: *note ver: XREFver, *note version: XREFversion.

 -- : V = version ()
 -- : [V, D] = version ()
 -- : V = version (FEATURE)
     Get version information for Octave.

     If called without input argument, the first return value V gives
     the version number of Octave as a string.  The second return value
     D holds the release date as a string.

     The following options can be passed for FEATURE:

     "-date"
          for the release date of the running build,

     "-description"
          for a description of the release (always an empty string),

     "-release"
          for the name of the running build (always an empty string),

     "-java"
          for version information of the Java VM,

     "-fftw"
          for version information for the linked FFTW,

     "-blas"
          for version information for the linked BLAS,

     "-lapack"
          for version information for the linked LAPACK.

     "-hgid"
          the mercurial ID of the sources used to build Octave.

     The variant with no input and output argument is an alias for the
     function ‘OCTAVE_VERSION’ provided for compatibility.

     See also: *note OCTAVE_VERSION: XREFOCTAVE_VERSION, *note ver:
     XREFver.

 -- : ver
 -- : ver Octave
 -- : ver PACKAGE
 -- : v = ver (...)

     Display a header containing the current Octave version number,
     license string, and operating system.  The header is followed by a
     list of installed packages, versions, and installation directories.

     Use the package name PACKAGE or Octave to limit the listing to a
     desired component.

     When called with an output argument, return a vector of structures
     describing Octave and each installed package.  The structure
     includes the following fields.

     ‘Name’
          Package name.

     ‘Version’
          Version of the package.

     ‘Release’
          Release of the package.

     ‘Date’
          Date of the version/release.

     See also: *note version: XREFversion, *note usejava: XREFusejava,
     *note pkg: XREFpkg.

 -- : compare_versions (V1, V2, OPERATOR)
     Compare two version strings using the given OPERATOR.

     This function assumes that versions V1 and V2 are arbitrarily long
     strings made of numeric and period characters possibly followed by
     an arbitrary string (e.g., "1.2.3", "0.3", "0.1.2+", or
     "1.2.3.4-test1").

     The version is first split into numeric and character portions and
     then the parts are padded to be the same length (i.e., "1.1" would
     be padded to be "1.1.0" when being compared with "1.1.1", and
     separately, the character parts of the strings are padded with
     nulls).

     The operator can be any logical operator from the set

        • "==" equal

        • "<" less than

        • "<=" less than or equal to

        • ">" greater than

        • ">=" greater than or equal to

        • "!=" not equal

        • "~=" not equal

     Note that version "1.1-test2" will compare as greater than
     "1.1-test10".  Also, since the numeric part is compared first, "a"
     compares less than "1a" because the second string starts with a
     numeric part even though ‘double ("a")’ is greater than ‘double
     ("1").’

 -- : license
 -- : license inuse
 -- : license inuse FEATURE
 -- : license ("inuse")
 -- : RETVAL = license ("inuse")
 -- : RETVAL = license ("test", FEATURE)
 -- : RETVAL = license ("checkout", FEATURE)
 -- : [RETVAL, ERRMSG] = license ("checkout", FEATURE)
     Get license information for Octave and Octave packages.

     GNU Octave is free software distributed under the GNU General
     Public License (GPL), and a license manager makes no sense.  This
     function is provided only for MATLAB compatibility.

     When called with no extra input arguments, it returns the Octave
     license, otherwise the first input defines the operation mode and
     must be one of the following strings: ‘inuse’, ‘test’, and
     ‘checkout’.  The optional FEATURE argument can either be "octave"
     (core), or an Octave package.

     "inuse"
          Returns a list of loaded features, i.e., octave and the list
          of loaded packages.  If an output is requested, it returns a
          struct array with the fields "feature", and "user".

     "test"
          Return true if the specified FEATURE is installed, false
          otherwise.

          An optional third argument "enable" or "disable" is accepted
          but ignored.

     "checkout"
          Return true if the specified FEATURE is installed, false
          otherwise.  An optional second output will have an error
          message if a package is not installed.

     See also: *note pkg: XREFpkg, *note ver: XREFver, *note version:
     XREFversion.

 -- : getrusage ()
     Return a structure containing a number of statistics about the
     current Octave process.

     Not all fields are available on all systems.  If it is not possible
     to get CPU time statistics, the CPU time slots are set to zero.
     Other missing data are replaced by NaN.  The list of possible
     fields is:

     ‘idrss’
          Unshared data size.

     ‘inblock’
          Number of block input operations.

     ‘isrss’
          Unshared stack size.

     ‘ixrss’
          Shared memory size.

     ‘majflt’
          Number of major page faults.

     ‘maxrss’
          Maximum data size.

     ‘minflt’
          Number of minor page faults.

     ‘msgrcv’
          Number of messages received.

     ‘msgsnd’
          Number of messages sent.

     ‘nivcsw’
          Number of involuntary context switches.

     ‘nsignals’
          Number of signals received.

     ‘nswap’
          Number of swaps.

     ‘nvcsw’
          Number of voluntary context switches.

     ‘oublock’
          Number of block output operations.

     ‘stime’
          A structure containing the system CPU time used.  The
          structure has the elements ‘sec’ (seconds) ‘usec’
          (microseconds).

     ‘utime’
          A structure containing the user CPU time used.  The structure
          has the elements ‘sec’ (seconds) ‘usec’ (microseconds).

 -- : VALUE = winqueryreg (ROOTKEY, SUBKEY, VALUENAME)
 -- : VALUE = winqueryreg (ROOTKEY, SUBKEY)
 -- : NAMES = winqueryreg (‘"name"’, ROOTKEY, SUBKEY)

     Query names or value from the Windows registry.

     On Windows, return the value of the registry key SUBKEY from the
     root key ROOTKEY.  You can specify the name of the queried registry
     value with the optional argument VALUENAME.  Otherwise, if called
     with only two arguments or VALUENAME is empty, then the default
     value of SUBKEY is returned.  If the registry value is of type
     "REG_DWORD" then VALUE is of class int32.  If the value is of the
     type "REG_SZ" or "REG_EXPAND_SZ" a string is returned.

     If the first argument is "name", a cell array of strings with the
     names of the values at that key is returned.

     The variable ROOTKEY must be a string with a valid root key
     identifier:

     HKCR
     HKEY_CLASSES_ROOT

     HKEY_CURRENT_CONFIG

     HKCU
     HKEY_CURRENT_USER

     HKLM
     HKEY_LOCAL_MACHINE

     HKU
     HKEY_USERS

     HKEY_PERFORMANCE_DATA

     Examples:

     Get a list of value names at the key ’HKCU\Environment’:

          VALUENAMES = winqueryreg ("name", "HKEY_CURRENT_USER", ...
                                    "Environment");

     For each VALUENAMES, display the value:

          for K = 1:numel (VALUENAMES)
            VAL = winqueryreg ("HKEY_CURRENT_USER", "Environment", ...
                               VALUENAMES{K});
            STR = sprintf ("%s = %s", VALUENAMES{K}, num2str (VAL));
            disp (STR);
          endfor

     On non-Windows platforms this function fails with an error.


File: octave.info,  Node: Hashing Functions,  Prev: System Information,  Up: System Utilities

36.12 Hashing Functions
=======================

It is often necessary to find if two strings or files are identical.
This might be done by comparing them character by character and looking
for differences.  However, this can be slow, and so comparing a hash of
the string or file can be a rapid way of finding if the files differ.

   Another use of the hashing function is to check for file integrity.
The user can check the hash of the file against a known value and find
if the file they have is the same as the one that the original hash was
produced with.

   Octave supplies the ‘hash’ function to calculate hash values of
strings and files, the latter in combination with the ‘fileread’
function.  The ‘hash’ function supports the most common used
cryptographic hash functions, namely MD5 and SHA-1.

 -- : hash (HFUN, STR)
     Calculate the hash value of the string STR using the hash function
     HFUN.

     The available hash functions are given in the table below.

     ‘MD2’
          Message-Digest Algorithm 2 (RFC 1319).

     ‘MD4’
          Message-Digest Algorithm 4 (RFC 1320).

     ‘MD5’
          Message-Digest Algorithm 5 (RFC 1321).

     ‘SHA1’
          Secure Hash Algorithm 1 (RFC 3174)

     ‘SHA224’
          Secure Hash Algorithm 2 (224 Bits, RFC 3874)

     ‘SHA256’
          Secure Hash Algorithm 2 (256 Bits, RFC 6234)

     ‘SHA384’
          Secure Hash Algorithm 2 (384 Bits, RFC 6234)

     ‘SHA512’
          Secure Hash Algorithm 2 (512 Bits, RFC 6234)

     To calculate for example the MD5 hash value of the string "abc" the
     ‘hash’ function is called as follows:

          hash ("md5", "abc")
               ⊣ ans = 900150983cd24fb0d6963f7d28e17f72

     For the same string, the SHA-1 hash value is calculated with:

          hash ("sha1", "abc")
               ⊣ ans = a9993e364706816aba3e25717850c26c9cd0d89d

     And to compute the hash value of a file, e.g., ‘file = "file.txt"’,
     call ‘hash’ in combination with the ‘fileread’:

          hash ("md5", fileread (file));


File: octave.info,  Node: Packages,  Next: External Code Interface,  Prev: System Utilities,  Up: Top

37 Packages
***********

Since Octave is Free Software users are encouraged to share their
programs with others.  To aid this sharing Octave supports the
installation of extra packages.  The ‘Octave Forge’ project is a
community-maintained set of packages that can be downloaded and
installed in Octave.  At the time of writing the ‘Octave Forge’ project
can be found online at <https://octave.sourceforge.io>, but since the
Internet is an ever-changing place this may not be true at the time of
reading.  Therefore it is recommended to see the Octave website for an
updated reference.

* Menu:

* Installing and Removing Packages::
* Using Packages::
* Administrating Packages::
* Creating Packages::


File: octave.info,  Node: Installing and Removing Packages,  Next: Using Packages,  Up: Packages

37.1 Installing and Removing Packages
=====================================

Assuming a package is available in the file ‘image-1.0.0.tar.gz’ it can
be installed from the Octave prompt with the command

     pkg install image-1.0.0.tar.gz

If the package is installed successfully nothing will be printed on the
prompt, but if an error occurred during installation it will be
reported.  It is possible to install several packages at once by writing
several package files after the ‘pkg install’ command.  If a different
version of the package is already installed it will be removed prior to
installing the new package.  This makes it easy to upgrade and downgrade
the version of a package, but makes it impossible to have several
versions of the same package installed at once.

   To see which packages are installed type

     pkg list
     ⊣ Package Name  | Version | Installation directory
     ⊣ --------------+---------+-----------------------
     ⊣        image *|   1.0.0 | /home/jwe/octave/image-1.0.0

In this case only version 1.0.0 of the ‘image’ package is installed.
The ’*’ character next to the package name shows that the image package
is loaded and ready for use.

   It is possible to remove a package from the system using the ‘pkg
uninstall’ command like this

     pkg uninstall image

If the package is removed successfully nothing will be printed in the
prompt, but if an error occurred it will be reported.  It should be
noted that the package file used for installation is not needed for
removal, and that only the package name as reported by ‘pkg list’ should
be used when removing a package.  It is possible to remove several
packages at once by writing several package names after the ‘pkg
uninstall’ command.

   To minimize the amount of code duplication between packages it is
possible that one package depends on another one.  If a package depends
on another, it will check if that package is installed during
installation.  If it is not, an error will be reported and the package
will not be installed.  This behavior can be disabled by passing the
‘-nodeps’ flag to the ‘pkg install’ command

     pkg install -nodeps my_package_with_dependencies.tar.gz

Since the installed package expects its dependencies to be installed it
may not function correctly.  Because of this it is not recommended to
disable dependency checking.

 -- : pkg COMMAND PKG_NAME
 -- : pkg COMMAND OPTION PKG_NAME
 -- : [OUT1, ...] = pkg (COMMAND, ... )
     Manage or query packages (groups of add-on functions) for Octave.

     Different actions are available depending on the value of COMMAND
     and on return arguments.

     Available commands:

     ‘install’
          Install named packages.  For example,

               pkg install image-1.0.0.tar.gz

          installs the package found in the file ‘image-1.0.0.tar.gz’.
          The file containing the package can be an url, e.g.

               pkg install 'http://somewebsite.org/image-1.0.0.tar.gz'

          installs the package found in the given url.  This requires an
          internet connection and the cURL library.

          _Security risk_: no verification of the package is performed
          before the installation.  It has the same security issues as
          manually downloading the package from the given url and
          installing it.

          _No support_: the GNU Octave community is not responsible for
          packages installed from foreign sites.  For support or for
          reporting bugs you need to contact the maintainers of the
          installed package directly (see the ‘DESCRIPTION’ file of the
          package)

          The OPTION variable can contain options that affect the manner
          in which a package is installed.  These options can be one or
          more of

          ‘-nodeps’
               The package manager will disable dependency checking.
               With this option it is possible to install a package even
               when it depends on another package which is not installed
               on the system.  *Use this option with care.*

          ‘-local’
               A local installation (package available only to current
               user) is forced, even if the user has system privileges.

          ‘-global’
               A global installation (package available to all users) is
               forced, even if the user doesn’t normally have system
               privileges.

          ‘-forge’
               Install a package directly from the Octave Forge
               repository.  This requires an internet connection and the
               cURL library.

               _Security risk_: no verification of the package is
               performed before the installation.  There are no
               signature for packages, or checksums to confirm the
               correct file was downloaded.  It has the same security
               issues as manually downloading the package from the
               Octave Forge repository and installing it.

          ‘-verbose’
               The package manager will print the output of all commands
               as they are performed.

     ‘update’
          Check installed Octave Forge packages against repository and
          update any outdated items.  This requires an internet
          connection and the cURL library.  Usage:

               pkg update

          To update a single package use ‘pkg install -forge’

     ‘uninstall’
          Uninstall named packages.  For example,

               pkg uninstall image

          removes the ‘image’ package from the system.  If another
          installed package depends on the ‘image’ package an error will
          be issued.  The package can be uninstalled anyway by using the
          ‘-nodeps’ option.

     ‘load’
          Add named packages to the path.  After loading a package it is
          possible to use the functions provided by the package.  For
          example,

               pkg load image

          adds the ‘image’ package to the path.

     ‘unload’
          Remove named packages from the path.  After unloading a
          package it is no longer possible to use the functions provided
          by the package.

     ‘list’
          Show the list of currently installed packages.  For example,

               pkg list

          will produce a short report with the package name, version,
          and installation directory for each installed package.  Supply
          a package name to limit reporting to a particular package.
          For example:

               pkg list image

          If a single return argument is requested then ‘pkg’ returns a
          cell array where each element is a structure with information
          on a single package.

               installed_packages = pkg ("list")

          If two output arguments are requested ‘pkg’ splits the list of
          installed packages into those which were installed by the
          current user, and those which were installed by the system
          administrator.

               [user_packages, system_packages] = pkg ("list")

          The "-forge" option lists packages available at the Octave
          Forge repository.  This requires an internet connection and
          the cURL library.  For example:

               oct_forge_pkgs = pkg ("list", "-forge")

     ‘describe’
          Show a short description of installed packages.  With the
          option "-verbose" also list functions provided by the package.
          For example,

               pkg describe -verbose

          will describe all installed packages and the functions they
          provide.  Display can be limited to a set of packages:

               ## describe control and signal packages
               pkg describe control signal

          If one output is requested a cell of structure containing the
          description and list of functions of each package is returned
          as output rather than printed on screen:

               desc = pkg ("describe", "secs1d", "image")

          If any of the requested packages is not installed, ‘pkg’
          returns an error, unless a second output is requested:

               [desc, flag] = pkg ("describe", "secs1d", "image")

          FLAG will take one of the values "Not installed", "Loaded", or
          "Not loaded" for each of the named packages.

     ‘prefix’
          Set the installation prefix directory.  For example,

               pkg prefix ~/my_octave_packages

          sets the installation prefix to ‘~/my_octave_packages’.
          Packages will be installed in this directory.

          It is possible to get the current installation prefix by
          requesting an output argument.  For example:

               pfx = pkg ("prefix")

          The location in which to install the architecture dependent
          files can be independently specified with an addition
          argument.  For example:

               pkg prefix ~/my_octave_packages ~/my_arch_dep_pkgs

     ‘local_list’
          Set the file in which to look for information on locally
          installed packages.  Locally installed packages are those that
          are available only to the current user.  For example:

               pkg local_list ~/.octave_packages

          It is possible to get the current value of local_list with the
          following

               pkg local_list

     ‘global_list’
          Set the file in which to look for information on globally
          installed packages.  Globally installed packages are those
          that are available to all users.  For example:

               pkg global_list /usr/share/octave/octave_packages

          It is possible to get the current value of global_list with
          the following

               pkg global_list

     ‘build’
          Build a binary form of a package or packages.  The binary file
          produced will itself be an Octave package that can be
          installed normally with ‘pkg’.  The form of the command to
          build a binary package is

               pkg build builddir image-1.0.0.tar.gz ...

          where ‘builddir’ is the name of a directory where the
          temporary installation will be produced and the binary
          packages will be found.  The options ‘-verbose’ and ‘-nodeps’
          are respected, while all other options are ignored.

     ‘rebuild’
          Rebuild the package database from the installed directories.
          This can be used in cases where the package database has been
          corrupted.

     See also: *note ver: XREFver, *note news: XREFnews.


File: octave.info,  Node: Using Packages,  Next: Administrating Packages,  Prev: Installing and Removing Packages,  Up: Packages

37.2 Using Packages
===================

By default installed packages are not available from the Octave prompt,
but it is possible to control this using the ‘pkg load’ and ‘pkg unload’
commands.  The functions from a package can be added to the Octave path
by typing

     pkg load package_name

where ‘package_name’ is the name of the package to be added to the path.

   In much the same way a package can be removed from the Octave path by
typing

     pkg unload package_name


File: octave.info,  Node: Administrating Packages,  Next: Creating Packages,  Prev: Using Packages,  Up: Packages

37.3 Administrating Packages
============================

On UNIX-like systems it is possible to make both per-user and
system-wide installations of a package.  If the user performing the
installation is ‘root’ the packages will be installed in a system-wide
directory that defaults to ‘OCTAVE_HOME/share/octave/packages/’.  If the
user is not ‘root’ the default installation directory is ‘~/octave/’.
Packages will be installed in a subdirectory of the installation
directory that will be named after the package.  It is possible to
change the installation directory by using the ‘pkg prefix’ command

     pkg prefix new_installation_directory

The current installation directory can be retrieved by typing

     current_installation_directory = pkg ("prefix")

   To function properly the package manager needs to keep some
information about the installed packages.  For per-user packages this
information is by default stored in the file ‘~/.octave_packages’ and
for system-wide installations it is stored in
‘OCTAVE_HOME/share/octave/octave_packages’.  The path to the per-user
file can be changed with the ‘pkg local_list’ command

     pkg local_list /path/to/new_file

For system-wide installations this can be changed in the same way using
the ‘pkg global_list’ command.  If these commands are called without a
new path, the current path will be returned.


File: octave.info,  Node: Creating Packages,  Prev: Administrating Packages,  Up: Packages

37.4 Creating Packages
======================

Internally a package is simply a gzipped tar file that contains a top
level directory of any given name.  This directory will in the following
be referred to as ‘package’ and may contain the following files:

‘package/CITATION’
     This is am optional file describing instructions on how to cite the
     package for publication.  It will be displayed verbatim by the
     function ‘citation’.

‘package/COPYING’
     This is a required file containing the license of the package.  No
     restrictions is made on the license in general.  If however the
     package contains dynamically linked functions the license must be
     compatible with the GNU General Public License.

‘package/DESCRIPTION’
     This is a required file containing information about the package.
     *Note The DESCRIPTION File::, for details on this file.

‘package/ChangeLog’
     This is an optional file describing all the changes made to the
     package source files.

‘package/INDEX’
     This is an optional file describing the functions provided by the
     package.  If this file is not given then one with be created
     automatically from the functions in the package and the
     ‘Categories’ keyword in the ‘DESCRIPTION’ file.  *Note The INDEX
     File::, for details on this file.

‘package/NEWS’
     This is an optional file describing all user-visible changes worth
     mentioning.  As this file increases on size, old entries can be
     moved into ‘package/ONEWS’.

‘package/ONEWS’
     This is an optional file describing old entries from the ‘NEWS’
     file.

‘package/PKG_ADD’
     An optional file that includes commands that are run when the
     package is added to the users path.  Note that ‘PKG_ADD’ directives
     in the source code of the package will also be added to this file
     by the Octave package manager.  Note that symbolic links are to be
     avoided in packages, as symbolic links do not exist on some file
     systems, and so a typical use for this file is the replacement of
     the symbolic link

          ln -s foo.oct bar.oct

     with an autoload directive like

          autoload ('bar', which ('foo'));

     *Note PKG_ADD and PKG_DEL Directives::, for details on ‘PKG_ADD’
     directives.

‘package/PKG_DEL’
     An optional file that includes commands that are run when the
     package is removed from the users path.  Note that ‘PKG_DEL’
     directives in the source code of the package will also be added to
     this file by the Octave package manager.  *Note PKG_ADD and PKG_DEL
     Directives::, for details on ‘PKG_DEL’ directives.

‘package/pre_install.m’
     This is an optional function that is run prior to the installation
     of a package.  This function is called with a single argument, a
     struct with fields names after the data in the ‘DESCRIPTION’, and
     the paths where the package functions will be installed.

‘package/post_install.m’
     This is an optional function that is run after the installation of
     a package.  This function is called with a single argument, a
     struct with fields names after the data in the ‘DESCRIPTION’, and
     the paths where the package functions were installed.

‘package/on_uninstall.m’
     This is an optional function that is run prior to the removal of a
     package.  This function is called with a single argument, a struct
     with fields names after the data in the ‘DESCRIPTION’, the paths
     where the package functions are installed, and whether the package
     is currently loaded.

   Besides the above mentioned files, a package can also contain one or
more of the following directories:

‘package/inst’
     An optional directory containing any files that are directly
     installed by the package.  Typically this will include any
     ‘m’-files.

‘package/src’
     An optional directory containing code that must be built prior to
     the packages installation.  The Octave package manager will execute
     ‘./configure’ in this directory if this script exists, and will
     then call ‘make’ if a file ‘Makefile’ exists in this directory.
     ‘make install’ will however not be called.  The environment
     variables ‘MKOCTFILE’, ‘OCTAVE_CONFIG’, and ‘OCTAVE’ will be set to
     the full paths of the programs ‘mkoctfile’, ‘octave-config’, and
     ‘octave’, respectively, of the correct version when ‘configure’ and
     ‘make’ are called.  If a file called ‘FILES’ exists all files
     listed there will be copied to the ‘inst’ directory, so they also
     will be installed.  If the ‘FILES’ file doesn’t exist, ‘src/*.m’
     and ‘src/*.oct’ will be copied to the ‘inst’ directory.

‘package/doc’
     An optional directory containing documentation for the package.
     The files in this directory will be directly installed in a
     sub-directory of the installed package for future reference.

‘package/bin’
     An optional directory containing files that will be added to the
     Octave ‘EXEC_PATH’ when the package is loaded.  This might contain
     external scripts, etc., called by functions within the package.

* Menu:

* The DESCRIPTION File::
* The INDEX File::
* PKG_ADD and PKG_DEL Directives::
* Missing Components::


File: octave.info,  Node: The DESCRIPTION File,  Next: The INDEX File,  Up: Creating Packages

37.4.1 The DESCRIPTION File
---------------------------

The ‘DESCRIPTION’ file contains various information about the package,
such as its name, author, and version.  This file has a very simple
format

   • Lines starting with ‘#’ are comments.

   • Lines starting with a blank character are continuations from the
     previous line.

   • Everything else is of the form ‘NameOfOption: ValueOfOption’.

The following is a simple example of a ‘DESCRIPTION’ file

     Name: The name of my package
     Version: 1.0.0
     Date: 2007-18-04
     Author: The name (and possibly email) of the package author.
     Maintainer: The name (and possibly email) of the current
      package maintainer.
     Title: The title of the package
     Description: A short description of the package.  If this
      description gets too long for one line it can continue
      on the next by adding a space to the beginning of the
      following lines.
     License: GPLv3+

   The package manager currently recognizes the following keywords

‘Name’
     Name of the package.

‘Version’
     Version of the package.  A package version must be 3 numbers
     separated by dots.

‘Date’
     Date of last update.

‘Author’
     Original author of the package.

‘Maintainer’
     Maintainer of the package.

‘Title’
     A one line description of the package.

‘Description’
     A one paragraph description of the package.

‘Categories’
     Optional keyword describing the package (if no ‘INDEX’ file is
     given this is mandatory).

‘Problems’
     Optional list of known problems.

‘Url’
     Optional list of homepages related to the package.

‘Depends’
     A list of other Octave packages that this package depends on.  This
     can include dependencies on particular versions, with a format

          Depends: package (>= 1.0.0)

     Possible operators are ‘<’, ‘<=’, ‘==’, ‘>=’ or ‘>’.  If the part
     of the dependency in ‘()’ is missing, any version of the package is
     acceptable.  Multiple dependencies can be defined as a comma
     separated list.

‘License’
     An optional short description of the used license (e.g., GPL
     version 3 or newer).  This is optional since the file ‘COPYING’ is
     mandatory.

‘SystemRequirements’
     These are the external install dependencies of the package and are
     not checked by the package manager.  This is here as a hint to the
     distribution packager.  They follow the same conventions as the
     ‘Depends’ keyword.

‘BuildRequires’
     These are the external build dependencies of the package and are
     not checked by the package manager.  This is here as a hint to the
     distribution packager.  They follow the same conventions as the
     ‘Depends’ keyword.  Note that in general, packaging systems such as
     ‘rpm’ or ‘deb’ autoprobe the install dependencies from the build
     dependencies, and therefore a ‘BuildRequires’ dependency usually
     removes the need for a ‘SystemRequirements’ dependency.

The developer is free to add additional arguments to the ‘DESCRIPTION’
file for their own purposes.  One further detail to aid the packager is
that the ‘SystemRequirements’ and ‘BuildRequires’ keywords can have a
distribution dependent section, and the automatic build process will use
these.  An example of the format of this is

     BuildRequires: libtermcap-devel [Mandriva] libtermcap2-devel

where the first package name will be used as a default and if the RPMs
are built on a Mandriva distribution, then the second package name will
be used instead.


File: octave.info,  Node: The INDEX File,  Next: PKG_ADD and PKG_DEL Directives,  Prev: The DESCRIPTION File,  Up: Creating Packages

37.4.2 The INDEX File
---------------------

The optional ‘INDEX’ file provides a categorical view of the functions
in the package.  This file has a very simple format

   • Lines beginning with ‘#’ are comments.

   • The first non-comment line should look like this

          toolbox >> Toolbox name

   • Lines beginning with an alphabetical character indicates a new
     category of functions.

   • Lines starting with a white space character indicate that the
     function names on the line belong to the last mentioned category.

The format can be summarized with the following example:

     # A comment
     toolbox >> Toolbox name
     Category Name 1
      function1 function2 function3
      function4
     Category Name 2
      function2 function5

   If you wish to refer to a function that users might expect to find in
your package but is not there, providing a work around or pointing out
that the function is available elsewhere, you can use:

     fn = workaround description

This workaround description will not appear when listing functions in
the package with ‘pkg describe’ but they will be published in the HTML
documentation online.  Workaround descriptions can use any HTML markup,
but keep in mind that it will be enclosed in a bold-italic environment.
For the special case of:

     fn = use <code>alternate expression</code>

the bold-italic is automatically suppressed.  You will need to use
‘<code>’ even in references:

     fn = use <a href="someothersite.html"><code>fn</code></a>

Sometimes functions are only partially compatible, in which case you can
list the non-compatible cases separately.  To refer to another function
in the package, use ‘<f>fn</f>’.  For example:

     eig (a, b) = use <f>qz</f>

Since sites may have many missing functions, you can define a macro
rather than typing the same link over and again.

     $id = expansion

defines the macro id.  You can use ‘$id’ anywhere in the description and
it will be expanded.  For example:

     $TSA = see <a href="link_to_spctools">SPC Tools</a>
     arcov = $TSA <code>armcv</code>

id is any string of letters, numbers and ‘_’.


File: octave.info,  Node: PKG_ADD and PKG_DEL Directives,  Next: Missing Components,  Prev: The INDEX File,  Up: Creating Packages

37.4.3 PKG_ADD and PKG_DEL Directives
-------------------------------------

If the package contains files called ‘PKG_ADD’ or ‘PKG_DEL’ the commands
in these files will be executed when the package is added or removed
from the users path.  In some situations such files are a bit cumbersome
to maintain, so the package manager supports automatic creation of such
files.  If a source file in the package contains a ‘PKG_ADD’ or
‘PKG_DEL’ directive they will be added to either the ‘PKG_ADD’ or
‘PKG_DEL’ files.

   In ‘m’-files a ‘PKG_ADD’ directive looks like this

     ## PKG_ADD: some_octave_command

Such lines should be added before the ‘function’ keyword.  In C++ files
a ‘PKG_ADD’ directive looks like this

     // PKG_ADD: some_octave_command

In both cases ‘some_octave_command’ should be replaced by the command
that should be placed in the ‘PKG_ADD’ file. ‘PKG_DEL’ directives work
in the same way, except the ‘PKG_ADD’ keyword is replaced with ‘PKG_DEL’
and the commands get added to the ‘PKG_DEL’ file.


File: octave.info,  Node: Missing Components,  Prev: PKG_ADD and PKG_DEL Directives,  Up: Creating Packages

37.4.4 Missing Components
-------------------------

If a package relies on a component, such as another Octave package, that
may not be present it may be useful to install a function which informs
users what to do when a particular component is missing.  The function
must be written by the package maintainer and registered with Octave
using ‘missing_component_hook’.

 -- : VAL = missing_component_hook ()
 -- : OLD_VAL = missing_component_hook (NEW_VAL)
 -- : missing_component_hook (NEW_VAL, "local")
     Query or set the internal variable that specifies the function to
     call when a component of Octave is missing.

     This can be useful for packagers that may split the Octave
     installation into multiple sub-packages, for example, to provide a
     hint to users for how to install the missing components.

     When called from inside a function with the "local" option, the
     variable is changed locally for the function and any subroutines it
     calls.  The original variable value is restored when exiting the
     function.

     The hook function is expected to be of the form

          FCN (COMPONENT)

     Octave will call FCN with the name of the function that requires
     the component and a string describing the missing component.  The
     hook function should return an error message to be displayed.

     See also: *note missing_function_hook: XREFmissing_function_hook.


File: octave.info,  Node: External Code Interface,  Next: Test and Demo Functions,  Prev: Packages,  Up: Top

Appendix A External Code Interface
**********************************

"The sum of human wisdom is not contained in any one language"

   — Ezra Pound

   Octave is a fantastic language for solving many problems in science
and engineering.  However, it is not the only computer language and
there are times when you may want to use code written in other
languages.  Good reasons for doing so include: 1) not re-inventing the
wheel; existing function libraries which have been thoroughly tested and
debugged or large scale simulation codebases are a good example, 2)
accessing unique capabilities of a different language; for example the
well-known regular expression functions of Perl (but don’t do that
because ‘regexp’ already exists in Octave).

   Performance should generally *not* be a reason for using compiled
extensions.  Although compiled extensions can run faster, particularly
if they replace a loop in Octave code, this is almost never the best
path to take.  First, there are many techniques to speed up Octave
performance while remaining within the language.  Second, Octave is a
high-level language that makes it easy to perform common mathematical
tasks.  Giving that up means shifting the focus from solving the real
problem to solving a computer programming problem.  It means returning
to low-level constructs such as pointers, memory management,
mathematical overflow/underflow, etc.  Because of the low level nature,
and the fact that the compiled code is executed outside of Octave, there
is the very real possibility of crashing the interpreter and losing
work.

   Before going further, you should first determine if you really need
to bother writing code outside of Octave.

   • Can I get the same functionality using the Octave scripting
     language alone?

     Even when a function already exists outside the language, it may be
     better to simply reproduce the behavior in an m-file rather than
     attempt to interface to the outside code.

   • Is the code thoroughly optimized for Octave?

     If performance is an issue you should always start with the
     in-language techniques for getting better performance.  Chief among
     these is vectorization (*note Vectorization and Faster Code
     Execution::) which not only makes the code concise and more
     understandable but improves performance (10X-100X). If loops must
     be used, make sure that the allocation of space for variables takes
     place outside the loops using an assignment to a matrix of the
     right size, or zeros.

   • Does the code make as much use as possible of existing built-in
     library routines?

     These routines are highly optimized and many do not carry the
     overhead of being interpreted.

   • Does writing a dynamically linked function represent a useful
     investment of your time, relative to staying in Octave?

     It will take time to learn Octave’s interface for external code and
     there will inevitably be issues with tools such as compilers.

   With that said, Octave offers a versatile interface for including
chunks of compiled code as dynamically linked extensions.  These
dynamically linked functions can be called from the interpreter in the
same manner as any ordinary function.  The interface is bi-directional
and external code can call Octave functions (like ‘plot’) which
otherwise might be very difficult to develop.

   The interface is centered around supporting the languages C++, C, and
Fortran.  Octave itself is written in C++ and can call external C++/C
code through its native oct-file interface.  The C language is also
supported through the mex-file interface for compatibility with MATLAB.
Fortran code is easiest to reach through the oct-file interface.

   Because many other languages provide C or C++ APIs it is relatively
simple to build bridges between Octave and other languages.  This is
also a way to bridge to hardware resources which often have device
drivers written in C.

* Menu:

* Oct-Files::
* Mex-Files::
* Standalone Programs::
* Java Interface::


File: octave.info,  Node: Oct-Files,  Next: Mex-Files,  Up: External Code Interface

A.1 Oct-Files
=============

* Menu:

* Getting Started with Oct-Files::
* Matrices and Arrays in Oct-Files::
* Character Strings in Oct-Files::
* Cell Arrays in Oct-Files::
* Structures in Oct-Files::
* Sparse Matrices in Oct-Files::
* Accessing Global Variables in Oct-Files::
* Calling Octave Functions from Oct-Files::
* Calling External Code from Oct-Files::
* Allocating Local Memory in Oct-Files::
* Input Parameter Checking in Oct-Files::
* Exception and Error Handling in Oct-Files::
* Documentation and Testing of Oct-Files::


File: octave.info,  Node: Getting Started with Oct-Files,  Next: Matrices and Arrays in Oct-Files,  Up: Oct-Files

A.1.1 Getting Started with Oct-Files
------------------------------------

Oct-files are pieces of C++ code that have been compiled with the Octave
API into a dynamically loadable object.  They take their name from the
file which contains the object which has the extension ‘.oct’.

   Finding a C++ compiler, using the correct switches, adding the right
include paths for header files, etc. is a difficult task.  Octave
automates this by providing the ‘mkoctfile’ command with which to build
oct-files.  The command is available from within Octave or at the shell
command line.

 -- : mkoctfile [-options] file ...
 -- : [OUTPUT, STATUS] = mkoctfile (...)

     The ‘mkoctfile’ function compiles source code written in C, C++, or
     Fortran.  Depending on the options used with ‘mkoctfile’, the
     compiled code can be called within Octave or can be used as a
     stand-alone application.

     ‘mkoctfile’ can be called from the shell prompt or from the Octave
     prompt.  Calling it from the Octave prompt simply delegates the
     call to the shell prompt.  The output is stored in the OUTPUT
     variable and the exit status in the STATUS variable.

     ‘mkoctfile’ accepts the following options, all of which are
     optional except for the filename of the code you wish to compile:

     ‘-I DIR’
          Add the include directory DIR to compile commands.

     ‘-D DEF’
          Add the definition DEF to the compiler call.

     ‘-l LIB’
          Add the library LIB to the link command.

     ‘-L DIR’
          Add the library directory DIR to the link command.

     ‘-M’
     ‘--depend’
          Generate dependency files (.d) for C and C++ source files.

     ‘-R DIR’
          Add the run-time path to the link command.

     ‘-Wl,...’
          Pass options to the linker like "-Wl,-rpath=...".  The quotes
          are needed since commas are interpreted as command separators.

     ‘-W...’
          Pass options to the assembler like "-Wa,OPTION".

     ‘-c’
          Compile but do not link.

     ‘-g’
          Enable debugging options for compilers.

     ‘-o FILE’
     ‘--output FILE’
          Output filename.  Default extension is .oct (or .mex if
          ‘--mex’ is specified) unless linking a stand-alone executable.

     ‘-p VAR’
     ‘--print VAR’
          Print configuration variable VAR.  There are three categories
          of variables:

          Octave configuration variables that users may override with
          environment variables.  These are used in commands that
          ‘mkoctfile’ executes.

                  ALL_CFLAGS                  LAPACK_LIBS
                  ALL_CXXFLAGS                LDFLAGS
                  ALL_FFLAGS                  LD_CXX
                  ALL_LDFLAGS                 LD_STATIC_FLAG
                  BLAS_LIBS                   LFLAGS
                  CC                          LIBDIR
                  CFLAGS                      LIBOCTAVE
                  CPICFLAG                    LIBOCTINTERP
                  CPPFLAGS                    OCTAVE_LINK_OPTS
                  CXX                         OCTINCLUDEDIR
                  CXXFLAGS                    OCTAVE_LIBS
                  CXXPICFLAG                  OCTAVE_LINK_DEPS
                  DL_LD                       OCTLIBDIR
                  DL_LDFLAGS                  OCT_LINK_DEPS
                  F77                         OCT_LINK_OPTS
                  F77_INTEGER8_FLAG           RDYNAMIC_FLAG
                  FFLAGS                      SPECIAL_MATH_LIB
                  FPICFLAG                    XTRA_CFLAGS
                  INCFLAGS                    XTRA_CXXFLAGS
                  INCLUDEDIR

          Octave configuration variables as above, but currently unused
          by ‘mkoctfile’.

                  AR
                  DEPEND_EXTRA_SED_PATTERN
                  DEPEND_FLAGS
                  FFTW3F_LDFLAGS
                  FFTW3F_LIBS
                  FFTW3_LDFLAGS
                  FFTW3_LIBS
                  FFTW_LIBS
                  FLIBS
                  LIBS
                  RANLIB
                  READLINE_LIBS

          Octave configuration variables that are provided for
          informational purposes only.  Except for ‘OCTAVE_HOME’ and
          ‘OCTAVE_EXEC_HOME’, users may not override these variables.

          If ‘OCTAVE_HOME’ or ‘OCTAVE_EXEC_HOME’ are set in the
          environment, then other variables are adjusted accordingly
          with ‘OCTAVE_HOME’ or ‘OCTAVE_EXEC_HOME’ substituted for the
          original value of the directory specified by the ‘--prefix’ or
          ‘--exec-prefix’ options that were used when Octave was
          configured.

                  API_VERSION                 LOCALFCNFILEDIR
                  ARCHLIBDIR                  LOCALOCTFILEDIR
                  BINDIR                      LOCALSTARTUPFILEDIR
                  CANONICAL_HOST_TYPE         LOCALVERARCHLIBDIR
                  DATADIR                     LOCALVERFCNFILEDIR
                  DATAROOTDIR                 LOCALVEROCTFILEDIR
                  DEFAULT_PAGER               MAN1DIR
                  EXEC_PREFIX                 MAN1EXT
                  EXEEXT                      MANDIR
                  FCNFILEDIR                  OCTAVE_EXEC_HOME
                  IMAGEDIR                    OCTAVE_HOME
                  INFODIR                     OCTAVE_VERSION
                  INFOFILE                    OCTDATADIR
                  LIBEXECDIR                  OCTDOCDIR
                  LOCALAPIARCHLIBDIR          OCTFILEDIR
                  LOCALAPIFCNFILEDIR          OCTFONTSDIR
                  LOCALAPIOCTFILEDIR          STARTUPFILEDIR
                  LOCALARCHLIBDIR

     ‘--link-stand-alone’
          Link a stand-alone executable file.

     ‘--mex’
          Assume we are creating a MEX file.  Set the default output
          extension to ".mex".

     ‘-s’
     ‘--strip’
          Strip the output file.

     ‘-v’
     ‘--verbose’
          Echo commands as they are executed.

     ‘file’
          The file to compile or link.  Recognized file types are:

                  .c    C source
                  .cc   C++ source
                  .cp   C++ source
                  .cpp  C++ source
                  .CPP  C++ source
                  .cxx  C++ source
                  .c++  C++ source
                  .C    C++ source
                  .f    Fortran source (fixed form)
                  .F    Fortran source (fixed form)
                  .f90  Fortran source (free form)
                  .F90  Fortran source (free form)
                  .o    object file
                  .a    library file

   Consider the following short example which introduces the basics of
writing a C++ function that can be linked to Octave.

     #include <octave/oct.h>
     
     DEFUN_DLD (helloworld, args, nargout,
                "Hello World Help String")
     {
       octave_stdout << "Hello World has "
                     << args.length () << " input arguments and "
                     << nargout << " output arguments.\n";
     
       // Return empty matrices for any outputs
       octave_value_list retval (nargout);
       for (int i = 0; i < nargout; i++)
         retval(i) = octave_value (Matrix ());
     
       return retval;
     }

   The first critical line is ‘#include <octave/oct.h>’ which makes
available most of the definitions necessary for a C++ oct-file.  Note
that ‘octave/oct.h’ is a C++ header and cannot be directly ‘#include’’ed
in a C source file, nor any other language.

   Included by ‘oct.h’ is a definition for the macro ‘DEFUN_DLD’ which
creates a dynamically loaded function.  This macro takes four arguments:

  1. The function name as it will be seen in Octave,

  2. The list of arguments to the function of type ‘octave_value_list’,

  3. The number of output arguments, which can be—and often is—omitted
     if not used, and

  4. The string to use for the help text of the function.

   The return type of functions defined with ‘DEFUN_DLD’ is always
‘octave_value_list’.

   There are a couple of important considerations in the choice of
function name.  First, it must be a valid Octave function name and so
must be a sequence of letters, digits, and underscores not starting with
a digit.  Second, as Octave uses the function name to define the
filename it attempts to find the function in, the function name in the
‘DEFUN_DLD’ macro must match the filename of the oct-file.  Therefore,
the above function should be in a file ‘helloworld.cc’, and would be
compiled to an oct-file using the command

     mkoctfile helloworld.cc

   This will create a file called ‘helloworld.oct’ that is the compiled
version of the function.  It should be noted that it is perfectly
acceptable to have more than one ‘DEFUN_DLD’ function in a source file.
However, there must either be a symbolic link to the oct-file for each
of the functions defined in the source code with the ‘DEFUN_DLD’ macro
or the ‘autoload’ (*note Function Files::) function should be used.

   The rest of the function shows how to find the number of input
arguments, how to print through the Octave pager, and how to return from
the function.  After compiling this function as above, an example of its
use is

     helloworld (1, 2, 3)
     ⊣ Hello World has 3 input arguments and 0 output arguments.

   Subsequent sections show how to use specific classes from Octave’s
core internals.  Base classes like ‘dMatrix’ (a matrix of double values)
are found in the directory ‘liboctave/array’.  The definitive reference
for how to use a particular class is the header file itself.  However,
it is often enough simply to study the examples in the manual in order
to be able to use a class.


File: octave.info,  Node: Matrices and Arrays in Oct-Files,  Next: Character Strings in Oct-Files,  Prev: Getting Started with Oct-Files,  Up: Oct-Files

A.1.2 Matrices and Arrays in Oct-Files
--------------------------------------

Octave supports a number of different array and matrix classes, the
majority of which are based on the ‘Array’ class.  The exception are the
sparse matrix types discussed separately below.  There are three basic
matrix types:

‘Matrix’
     A double precision matrix class defined in ‘dMatrix.h’

‘ComplexMatrix’
     A complex matrix class defined in ‘CMatrix.h’

‘BoolMatrix’
     A boolean matrix class defined in ‘boolMatrix.h’

   These are the basic two-dimensional matrix types of Octave.  In
addition there are a number of multi-dimensional array types including

‘NDArray’
     A double precision array class defined in ‘dNDArray.h’

‘ComplexNDarray’
     A complex array class defined in ‘CNDArray.h’

‘boolNDArray’
     A boolean array class defined in ‘boolNDArray.h’

‘int8NDArray’
‘int16NDArray’
‘int32NDArray’
‘int64NDArray’
     8, 16, 32, and 64-bit signed array classes defined in
     ‘int8NDArray.h’, ‘int16NDArray.h’, etc.

‘uint8NDArray’
‘uint16NDArray’
‘uint32NDArray’
‘uint64NDArray’
     8, 16, 32, and 64-bit unsigned array classes defined in
     ‘uint8NDArray.h’, ‘uint16NDArray.h’, etc.

   There are several basic ways of constructing matrices or
multi-dimensional arrays.  Using the class ‘Matrix’ as an example one
can

   • Create an empty matrix or array with the empty constructor.  For
     example:

          Matrix a;

     This can be used for all matrix and array types.

   • Define the dimensions of the matrix or array with a dim_vector
     which has the same characteristics as the vector returned from
     ‘size’.  For example:

          dim_vector dv (2, 3);  // 2 rows, 3 columns
          Matrix a (dv);

     This can be used for all matrix and array types.

   • Define the number of rows and columns in the matrix.  For example:

          Matrix a (2, 2)

     This constructor can *only* be used with matrix types.

   These types all share a number of basic methods and operators.  Many
bear a resemblance to functions that exist in the interpreter.  A
selection of useful methods include

 -- Method: T& operator () (octave_idx_type)
 -- Method: T& elem (octave_idx_type)
     The ‘()’ operator or ‘elem’ method allow the values of the matrix
     or array to be read or set.  These methods take a single argument,
     which is of type ‘octave_idx_type’, that is the index into the
     matrix or array.  Additionally, the matrix type allows two argument
     versions of the ‘()’ operator and ‘elem’ method, giving the row and
     column index of the value to get or set.

   Note that these functions do significant error checking and so in
some circumstances the user might prefer to access the data of the array
or matrix directly through the ‘fortran_vec’ method discussed below.

 -- Method: octave_idx_type numel (void) const
     The total number of elements in the matrix or array.

 -- Method: size_t byte_size (void) const
     The number of bytes used to store the matrix or array.

 -- Method: dim_vector dims (void) const
     The dimensions of the matrix or array in value of type
     ‘dim_vector’.

 -- Method: int ndims (void) const
     The number of dimensions of the matrix or array.  Matrices are
     always 2-D, but arrays can be N-dimensional.

 -- Method: void resize (const dim_vector&)
 -- Method: void resize (nrows, ncols)
     A method taking either an argument of type ‘dim_vector’, or, in the
     case of a matrix, two arguments of type ‘octave_idx_type’ defining
     the number of rows and columns in the matrix.

 -- Method: T* fortran_vec (void)
     This method returns a pointer to the underlying data of the matrix
     or array so that it can be manipulated directly, either within
     Octave or by an external library.

   Operators such as ‘+’, ‘-’, or ‘*’ can be used on the majority of the
matrix and array types.  In addition there are a number of methods that
are of interest only for matrices such as ‘transpose’, ‘hermitian’,
‘solve’, etc.

   The typical way to extract a matrix or array from the input arguments
of ‘DEFUN_DLD’ function is as follows

     #include <octave/oct.h>
     
     DEFUN_DLD (addtwomatrices, args, , "Add A to B")
     {
       if (args.length () != 2)
         print_usage ();
     
       NDArray A = args(0).array_value ();
       NDArray B = args(1).array_value ();
     
       return octave_value (A + B);
     }

   To avoid segmentation faults causing Octave to abort, this function
explicitly checks that there are sufficient arguments available before
accessing these arguments.  It then obtains two multi-dimensional arrays
of type ‘NDArray’ and adds these together.  Note that the ‘array_value’
method is called without using the ‘is_matrix_type’ method.  If an error
occurs when attempting to extract the value, Octave will print a message
and throw an exception.  The reason to prefer this coding structure is
that the arguments might be a type which is not an ‘NDArray’, but for
which it would make sense to convert them to one.  The ‘array_value’
method allows this conversion to be performed transparently when
possible.  If you need to catch errors like this, and perform some kind
of cleanup or other operation, you can catch the
‘octave_execution_error’ exception.

   ‘A + B’, operating on two ‘NDArray’ objects returns an ‘NDArray’,
which is cast to an ‘octave_value’ on the return from the function.  An
example of the use of this demonstration function is

     addtwomatrices (ones (2, 2), eye (2, 2))
           ⇒  2  1
               1  2

   A list of the basic ‘Matrix’ and ‘Array’ types, the methods to
extract these from an ‘octave_value’, and the associated header file is
listed below.

Type                   Function                      Source Code
----------------------------------------------------------------------------
‘RowVector’            ‘row_vector_value’            ‘dRowVector.h’
‘ComplexRowVector’     ‘complex_row_vector_value’    ‘CRowVector.h’
‘ColumnVector’         ‘column_vector_value’         ‘dColVector.h’
‘ComplexColumnVector’  ‘complex_column_vector_value’ ‘CColVector.h’
‘Matrix’               ‘matrix_value’                ‘dMatrix.h’
‘ComplexMatrix’        ‘complex_matrix_value’        ‘CMatrix.h’
‘boolMatrix’           ‘bool_matrix_value’           ‘boolMatrix.h’
‘charMatrix’           ‘char_matrix_value’           ‘chMatrix.h’
‘NDArray’              ‘array_value’                 ‘dNDArray.h’
‘ComplexNDArray’       ‘complex_array_value’         ‘CNDArray.h’
‘boolNDArray’          ‘bool_array_value’            ‘boolNDArray.h’
‘charNDArray’          ‘char_array_value’            ‘charNDArray.h’
‘int8NDArray’          ‘int8_array_value’            ‘int8NDArray.h’
‘int16NDArray’         ‘int16_array_value’           ‘int16NDArray.h’
‘int32NDArray’         ‘int32_array_value’           ‘int32NDArray.h’
‘int64NDArray’         ‘int64_array_value’           ‘int64NDArray.h’
‘uint8NDArray’         ‘uint8_array_value’           ‘uint8NDArray.h’
‘uint16NDArray’        ‘uint16_array_value’          ‘uint16NDArray.h’
‘uint32NDArray’        ‘uint32_array_value’          ‘uint32NDArray.h’
‘uint64NDArray’        ‘uint64_array_value’          ‘uint64NDArray.h’


File: octave.info,  Node: Character Strings in Oct-Files,  Next: Cell Arrays in Oct-Files,  Prev: Matrices and Arrays in Oct-Files,  Up: Oct-Files

A.1.3 Character Strings in Oct-Files
------------------------------------

A character string in Octave is just a special ‘Array’ class.  Consider
the example:

     #include <octave/oct.h>
     
     DEFUN_DLD (stringdemo, args, , "String Demo")
     {
       if (args.length () != 1)
         print_usage ();
     
       octave_value_list retval;
     
       charMatrix ch = args(0).char_matrix_value ();
     
       retval(1) = octave_value (ch, '\'');  // Single Quote String
     
       octave_idx_type nr = ch.rows ();
     
       for (octave_idx_type i = 0; i < nr / 2; i++)
         {
           std::string tmp = ch.row_as_string (i);
     
           ch.insert (ch.row_as_string (nr-i-1).c_str (), i, 0);
           ch.insert (tmp.c_str (), nr-i-1, 0);
         }
     
       retval(0) = octave_value (ch, '"');  // Double Quote String
     
       return retval;
     }

   An example of the use of this function is

     s0 = ["First String"; "Second String"];
     [s1,s2] = stringdemo (s0)
     ⇒ s1 = Second String
             First String

     ⇒ s2 = First String
             Second String

     typeinfo (s2)
     ⇒ sq_string
     typeinfo (s1)
     ⇒ string

   One additional complication of strings in Octave is the difference
between single quoted and double quoted strings.  To find out if an
‘octave_value’ contains a single or double quoted string use one of the
predicate tests shown below.

     if (args(0).is_sq_string ())
       octave_stdout << "First argument is a single quoted string\n";
     else if (args(0).is_dq_string ())
       octave_stdout << "First argument is a double quoted string\n";

   Note, however, that both types of strings are represented by the
‘charNDArray’ type, and so when assigning to an ‘octave_value’, the type
of string should be specified.  For example:

     octave_value_list retval;
     charNDArray ch;
     ...
     // Create single quoted string
     retval(1) = octave_value (ch);   // default constructor is sq_string
                OR
     retval(1) = octave_value (ch, '\'');  // explicitly create sq_string

     // Create a double quoted string
     retval(0) = octave_value (ch, '"');


File: octave.info,  Node: Cell Arrays in Oct-Files,  Next: Structures in Oct-Files,  Prev: Character Strings in Oct-Files,  Up: Oct-Files

A.1.4 Cell Arrays in Oct-Files
------------------------------

Octave’s cell type is also available from within oct-files.  A cell
array is just an ‘Array’ of ‘octave_value’s, and thus each element of
the cell array can be treated like any other ‘octave_value’.  A simple
example is

     #include <octave/oct.h>
     #include <octave/Cell.h>
     
     DEFUN_DLD (celldemo, args, , "Cell Demo")
     {
       if (args.length () != 1)
         print_usage ();
     
       Cell c = args(0).cell_value ();
     
       octave_value_list retval;
       retval.resize (c.numel ());    // faster code by pre-declaring size
     
       for (octave_idx_type i = 0; i < c.numel (); i++)
         {
           retval(i) = c(i);          // using operator syntax
           //retval(i) = c.elem (i);  // using method syntax
         }
     
       return retval;
     }

   Note that cell arrays are used less often in standard oct-files and
so the ‘Cell.h’ header file must be explicitly included.  The rest of
the example extracts the ‘octave_value’s one by one from the cell array
and returns them as individual output arguments.  For example:

     [b1, b2, b3] = celldemo ({1, [1, 2], "test"})
     ⇒
     b1 =  1
     b2 =

        1   2

     b3 = test


File: octave.info,  Node: Structures in Oct-Files,  Next: Sparse Matrices in Oct-Files,  Prev: Cell Arrays in Oct-Files,  Up: Oct-Files

A.1.5 Structures in Oct-Files
-----------------------------

A structure in Octave is a map between a number of fields represented
and their values.  The Standard Template Library ‘map’ class is used,
with the pair consisting of a ‘std::string’ and an Octave ‘Cell’
variable.

   A simple example demonstrating the use of structures within oct-files
is

     #include <octave/oct.h>
     #include <octave/ov-struct.h>
     
     DEFUN_DLD (structdemo, args, , "Struct Demo")
     {
       if (args.length () != 2)
         print_usage ();
     
       if (! args(0).isstruct ())
         error ("structdemo: ARG1 must be a struct");
     
       octave_scalar_map arg0 = args(0).scalar_map_value ();
       //octave_map arg0 = args(0).map_value ();
     
       if (! args(1).is_string ())
         error ("structdemo: ARG2 must be a character string");
     
       std::string arg1 = args(1).string_value ();
     
       octave_value tmp = arg0.contents (arg1);
       //octave_value tmp = arg0.contents (arg1)(0);
     
       if (! tmp.is_defined ())
         error ("structdemo: struct does not have a field named '%s'\n",
                arg1.c_str ());
     
       octave_scalar_map st;
     
       st.assign ("selected", tmp);
     
       return octave_value (st);
     }

   An example of its use is

     x.a = 1; x.b = "test"; x.c = [1, 2];
     structdemo (x, "b")
     ⇒ selected = test

   The example above specifically uses the ‘octave_scalar_map’ class
which is for representing a single struct.  For structure arrays, the
‘octave_map’ class is used instead.  The commented code shows how the
demo could be modified to handle a structure array.  In that case, the
‘contents’ method returns a ‘Cell’ which may have more than one element.
Therefore, to obtain the underlying ‘octave_value’ in the single struct
example we would write

     octave_value tmp = arg0.contents (arg1)(0);

where the trailing ‘(0)’ is the ‘()’ operator on the ‘Cell’ object.  If
this were a true structure array with multiple elements we could iterate
over the elements using the ‘()’ operator.

   Structures are a relatively complex data container and there are more
functions available in ‘oct-map.h’ which make coding with them easier
than relying on just ‘contents’.


File: octave.info,  Node: Sparse Matrices in Oct-Files,  Next: Accessing Global Variables in Oct-Files,  Prev: Structures in Oct-Files,  Up: Oct-Files

A.1.6 Sparse Matrices in Oct-Files
----------------------------------

There are three classes of sparse objects that are of interest to the
user.

‘SparseMatrix’
     A double precision sparse matrix class

‘SparseComplexMatrix’
     A complex sparse matrix class

‘SparseBoolMatrix’
     A boolean sparse matrix class

   All of these classes inherit from the ‘Sparse<T>’ template class, and
so all have similar capabilities and usage.  The ‘Sparse<T>’ class was
based on Octave’s ‘Array<T>’ class and users familiar with Octave’s
‘Array’ classes will be comfortable with the use of the sparse classes.

   The sparse classes will not be entirely described in this section,
due to their similarity with the existing ‘Array’ classes.  However,
there are a few differences due the nature of sparse objects, and these
will be described.  First, although it is fundamentally possible to have
N-dimensional sparse objects, the Octave sparse classes do not allow
them at this time; All instances of the sparse classes *must* be
2-dimensional.  This means that ‘SparseMatrix’ is actually more similar
to Octave’s ‘Matrix’ class than it is to the ‘NDArray’ class.

* Menu:

* Array and Sparse Class Differences::
* Creating Sparse Matrices in Oct-Files::
* Using Sparse Matrices in Oct-Files::


File: octave.info,  Node: Array and Sparse Class Differences,  Next: Creating Sparse Matrices in Oct-Files,  Up: Sparse Matrices in Oct-Files

A.1.6.1 Array and Sparse Class Differences
..........................................

The number of elements in a sparse matrix is considered to be the number
of nonzero elements, rather than the product of the dimensions.
Therefore,

     SparseMatrix sm;
     ...
     int nnz = sm.nelem ();

returns the number of nonzero elements (like the interpreter function
‘nnz’).  If the user really requires the number of elements in the
matrix, including the nonzero elements, they should use ‘numel’ rather
than ‘nelem’.  Note that for very large matrices, where the product of
the two dimensions is larger than the representation of an unsigned int,
‘numel’ can overflow.  An example is ‘speye (1e6)’ which will create a
matrix with a million rows and columns, but only a million nonzero
elements.  In this case, the number of rows multiplied by the number of
columns is more than two hundred times the maximum value that can be
represented by an unsigned 32-bit int.  The use of ‘numel’ should,
therefore, be avoided unless it is known that it will not overflow.

   Extreme care is also required when using the ‘elem’ method or the
‘()’ operator which perform essentially the same function.  The reason
is that if a sparse object is non-const, then Octave will assume that a
request for a zero element in a sparse matrix is in fact a request to
create this element so it can be filled.  Therefore, a piece of code
like

     SparseMatrix sm;
     ...
     for (int j = 0; j < nc; j++)
       for (int i = 0; i < nr; i++)
         std::cerr << " (" << i << "," << j << "): " << sm(i,j) << "\n";

is a great way of turning a sparse matrix into a dense one, and a very
slow way at that since it reallocates the sparse object for each zero
element in the matrix.

   A simple way of preventing the above from happening is to create a
temporary constant version of the sparse matrix.  Note that only the
container for the sparse matrix will be copied, while the actual
representation of the data will be shared between the two versions of
the sparse matrix; This is not a costly operation.  The example above,
re-written to prevent sparse-to-dense conversion, is

     SparseMatrix sm;
     ...
     const SparseMatrix tmp (sm);
     for (int j = 0; j < nc; j++)
       for (int i = 0; i < nr; i++)
         std::cerr << " (" << i << "," << j << "): " << tmp(i,j) << "\n";

   Finally, because the sparse types aren’t represented by a contiguous
block of memory, the ‘fortran_vec’ method of ‘Array<T>’ is not
available.  It is, however, replaced by three separate methods ‘ridx’,
‘cidx’, and ‘data’, that access the raw compressed column format that
Octave sparse matrices are stored in.  These methods can be used in a
manner similar to ‘elem’ to allow the matrix to be accessed or filled.
However, it is up to the user to respect the sparse matrix compressed
column format or the matrix will become corrupted.


File: octave.info,  Node: Creating Sparse Matrices in Oct-Files,  Next: Using Sparse Matrices in Oct-Files,  Prev: Array and Sparse Class Differences,  Up: Sparse Matrices in Oct-Files

A.1.6.2 Creating Sparse Matrices in Oct-Files
.............................................

There are two useful strategies for creating a sparse matrix.  The first
is to create three vectors representing the row index, column index, and
data values, and from these create the matrix.  The second alternative
is to create a sparse matrix with the appropriate amount of space, and
then fill in the values.  Both techniques have their advantages and
disadvantages.

   Below is an example of creating a small sparse matrix using the first
technique

     int nz, nr, nc;
     nz = 4, nr = 3, nc = 4;

     ColumnVector ridx (nz);
     ColumnVector cidx (nz);
     ColumnVector data (nz);

     ridx(0) = 1; cidx(0) = 1; data(0) = 1;
     ridx(1) = 2; cidx(1) = 2; data(1) = 2;
     ridx(2) = 2; cidx(2) = 4; data(2) = 3;
     ridx(3) = 3; cidx(3) = 4; data(3) = 4;
     SparseMatrix sm (data, ridx, cidx, nr, nc);

which creates the matrix given in section *note Storage of Sparse
Matrices::.  Note that the compressed matrix format is not used at the
time of the creation of the matrix itself, but is used internally.

   As discussed in the chapter on Sparse Matrices, the values of the
sparse matrix are stored in increasing column-major ordering.  Although
the data passed by the user need not respect this requirement,
pre-sorting the data will significantly speed up creation of the sparse
matrix.

   The disadvantage of this technique for creating a sparse matrix is
that there is a brief time when two copies of the data exist.  For
extremely memory constrained problems this may not be the best technique
for creating a sparse matrix.

   The alternative is to first create a sparse matrix with the desired
number of nonzero elements and then later fill those elements in.
Sample code:

     int nz, nr, nc;
     nz = 4, nr = 3, nc = 4;
     SparseMatrix sm (nr, nc, nz);
     sm(0,0) = 1; sm(0,1) = 2; sm(1,3) = 3; sm(2,3) = 4;

   This creates the same matrix as previously.  Again, although not
strictly necessary, it is significantly faster if the sparse matrix is
created and the elements are added in column-major ordering.  The reason
for this is that when elements are inserted at the end of the current
list of known elements then no element in the matrix needs to be moved
to allow the new element to be inserted; Only the column indices need to
be updated.

   There are a few further points to note about this method of creating
a sparse matrix.  First, it is possible to create a sparse matrix with
fewer elements than are actually inserted in the matrix.  Therefore,

     int nr, nc;
     nr = 3, nc = 4;
     SparseMatrix sm (nr, nc, 0);
     sm(0,0) = 1; sm(0,1) = 2; sm(1,3) = 3; sm(2,3) = 4;

is perfectly valid.  However, it is a very bad idea because as each new
element is added to the sparse matrix the matrix needs to request more
space and reallocate memory.  This is an expensive operation that will
significantly slow this means of creating a sparse matrix.  It is
possible to create a sparse matrix with excess storage, so having NZ
greater than 4 in this example is also valid.  The disadvantage is that
the matrix occupies more memory than strictly needed.

   Of course, it is not always possible to know the number of nonzero
elements prior to filling a matrix.  For this reason the additional
unused storage of a sparse matrix can be removed after its creation with
the ‘maybe_compress’ function.  In addition to deallocating unused
storage, ‘maybe_compress’ can also remove zero elements from the matrix.
The removal of zero elements from the matrix is controlled by setting
the argument of the ‘maybe_compress’ function to be ‘true’.  However,
the cost of removing the zeros is high because it implies re-sorting the
elements.  If possible, it is better for the user to avoid adding the
unnecessary zeros in the first place.  An example of the use of
‘maybe_compress’ is

     int nz, nr, nc;
     nz = 6, nr = 3, nc = 4;

     SparseMatrix sm1 (nr, nc, nz);
     sm1(0,0) = 1; sm1(0,1) = 2; sm1(1,3) = 3; sm1(2,3) = 4;
     sm1.maybe_compress ();   // No zero elements were added

     SparseMatrix sm2 (nr, nc, nz);
     sm2(0,0) = 1; sm2(0,1) = 2; sm(0,2) = 0; sm(1,2) = 0;
     sm1(1,3) = 3; sm1(2,3) = 4;
     sm2.maybe_compress (true);  // Zero elements were added

   The use of the ‘maybe_compress’ function should be avoided if
possible as it will slow the creation of the matrix.

   A third means of creating a sparse matrix is to work directly with
the data in compressed row format.  An example of this advanced
technique might be

     octave_value arg;
     ...
     int nz, nr, nc;
     nz = 6, nr = 3, nc = 4;   // Assume we know the max # nz
     SparseMatrix sm (nr, nc, nz);
     Matrix m = arg.matrix_value ();

     int ii = 0;
     sm.cidx (0) = 0;
     for (int j = 1; j < nc; j++)
       {
         for (int i = 0; i < nr; i++)
           {
             double tmp = m(i,j);
             if (tmp != 0.)
               {
                 sm.data(ii) = tmp;
                 sm.ridx(ii) = i;
                 ii++;
               }
           }
         sm.cidx(j+1) = ii;
      }
     sm.maybe_compress ();  // If don't know a priori the final # of nz.

which is probably the most efficient means of creating a sparse matrix.

   Finally, it may sometimes arise that the amount of storage initially
created is insufficient to completely store the sparse matrix.
Therefore, the method ‘change_capacity’ exists to reallocate the sparse
memory.  The above example would then be modified as

     octave_value arg;
     ...
     int nz, nr, nc;
     nz = 6, nr = 3, nc = 4;   // Guess the number of nz elements
     SparseMatrix sm (nr, nc, nz);
     Matrix m = arg.matrix_value ();

     int ii = 0;
     sm.cidx (0) = 0;
     for (int j = 1; j < nc; j++)
       {
         for (int i = 0; i < nr; i++)
           {
             double tmp = m(i,j);
             if (tmp != 0.)
               {
                 if (ii == nz)
                   {
                     nz += 2;   // Add 2 more elements
                     sm.change_capacity (nz);
                   }
                 sm.data(ii) = tmp;
                 sm.ridx(ii) = i;
                 ii++;
               }
           }
         sm.cidx(j+1) = ii;
      }
     sm.maybe_compress ();  // If don't know a priori the final # of nz.

   Note that both increasing and decreasing the number of nonzero
elements in a sparse matrix is expensive as it involves memory
reallocation.  Also because parts of the matrix, though not its
entirety, exist as old and new copies at the same time, additional
memory is needed.  Therefore, if possible avoid changing capacity.


File: octave.info,  Node: Using Sparse Matrices in Oct-Files,  Prev: Creating Sparse Matrices in Oct-Files,  Up: Sparse Matrices in Oct-Files

A.1.6.3 Using Sparse Matrices in Oct-Files
..........................................

Most of the same operators and functions for sparse matrices that are
available from the Octave interpreter are also available within
oct-files.  The basic means of extracting a sparse matrix from an
‘octave_value’, and returning it as an ‘octave_value’, can be seen in
the following example.

     octave_value_list retval;

     SparseMatrix sm = args(0).sparse_matrix_value ();
     SparseComplexMatrix scm = args(1).sparse_complex_matrix_value ();
     SparseBoolMatrix sbm = args(2).sparse_bool_matrix_value ();
     ...
     retval(2) = sbm;
     retval(1) = scm;
     retval(0) = sm;

   The conversion to an ‘octave_value’ is handled by the sparse
‘octave_value’ constructors, and so no special care is needed.


File: octave.info,  Node: Accessing Global Variables in Oct-Files,  Next: Calling Octave Functions from Oct-Files,  Prev: Sparse Matrices in Oct-Files,  Up: Oct-Files

A.1.7 Accessing Global Variables in Oct-Files
---------------------------------------------

Global variables allow variables in the global scope to be accessed.
Global variables can be accessed within oct-files by using the support
functions ‘get_global_value’ and ‘set_global_value’. ‘get_global_value’
takes two arguments, the first is a string representing the variable
name to obtain.  The second argument is a boolean argument specifying
what to do if no global variable of the desired name is found.  An
example of the use of these two functions is

     #include <octave/oct.h>
     
     DEFUN_DLD (globaldemo, args, , "Global Demo")
     {
       if (args.length () != 1)
         print_usage ();
     
       octave_value retval;
     
       std::string s = args(0).string_value ();
     
       octave_value tmp = get_global_value (s, true);
     
       if (tmp.is_defined ())
         retval = tmp;
       else
         retval = "Global variable not found";
     
       set_global_value ("a", 42.0);
     
       return retval;
     }

   An example of its use is

     global a b
     b = 10;
     globaldemo ("b")
     ⇒ 10
     globaldemo ("c")
     ⇒ "Global variable not found"
     num2str (a)
     ⇒ 42


File: octave.info,  Node: Calling Octave Functions from Oct-Files,  Next: Calling External Code from Oct-Files,  Prev: Accessing Global Variables in Oct-Files,  Up: Oct-Files

A.1.8 Calling Octave Functions from Oct-Files
---------------------------------------------

There is often a need to be able to call another Octave function from
within an oct-file, and there are many examples of such within Octave
itself.  For example, the ‘quad’ function is an oct-file that calculates
the definite integral by quadrature over a user-supplied function.

   There are also many ways in which a function could be given as input.
It might be passed as one of

  1. Function Handle

  2. Anonymous Function Handle

  3. Inline Function

  4. String

   The code below demonstrates all four methods of passing a function to
an oct-file.

     #include <octave/oct.h>
     #include <octave/parse.h>
     
     DEFUN_DLD (funcdemo, args, nargout, "Function Demo")
     {
       int nargin = args.length ();
     
       if (nargin < 2)
         print_usage ();
     
       octave_value_list newargs;
     
       for (octave_idx_type i = nargin - 1; i > 0; i--)
         newargs(i-1) = args(i);
     
       octave_value_list retval;
     
       if (args(0).is_function_handle () || args(0).is_inline_function ())
         {
           octave_function *fcn = args(0).function_value ();
     
           retval = feval (fcn, newargs, nargout);
         }
       else if (args(0).is_string ())
         {
           std::string fcn = args(0).string_value ();
     
           retval = feval (fcn, newargs, nargout);
         }
       else
         error ("funcdemo: INPUT must be string, inline, or function handle");
     
       return retval;
     }

   The first input to the demonstration code is a user-supplied function
and the remaining arguments are all passed to the function.

     funcdemo (@sin, 1)
     ⇒ 0.84147
     funcdemo (@(x) sin (x), 1)
     ⇒ 0.84147
     funcdemo (inline ("sin (x)"), 1)
     ⇒ 0.84147
     funcdemo ("sin", 1)
     ⇒ 0.84147
     funcdemo (@atan2, 1, 1)
     ⇒ 0.78540

   When the user function is passed as a string the treatment of the
function is different.  In some cases it is necessary to have the user
supplied function as an ‘octave_function’ object.  In that case the
string argument can be used to create a temporary function as
demonstrated below.

     std::octave fcn_name = unique_symbol_name ("__fcn__");
     std::string fcode = "function y = ";
     fcode.append (fcn_name);
     fcode.append ("(x) y = ");
     fcn = extract_function (args(0), "funcdemo", fcn_name,
                             fcode, "; endfunction");
     ...
     if (fcn_name.length ())
       clear_function (fcn_name);

   There are two important things to know in this case.  First, the
number of input arguments to the user function is fixed, and in the
above example is a single argument.  Second, to avoid leaving the
temporary function in the Octave symbol table it should be cleared after
use.  Also, by convention all internal function names begin and end with
the character sequence ‘__’.


File: octave.info,  Node: Calling External Code from Oct-Files,  Next: Allocating Local Memory in Oct-Files,  Prev: Calling Octave Functions from Oct-Files,  Up: Oct-Files

A.1.9 Calling External Code from Oct-Files
------------------------------------------

Linking external C code to Octave is relatively simple, as the C
functions can easily be called directly from C++.  One possible issue is
that the declarations of the external C functions may need to be
explicitly defined as C functions to the compiler.  If the declarations
of the external C functions are in the header ‘foo.h’, then the tactic
to ensure that the C++ compiler treats these declarations as C code is

     #ifdef __cplusplus
     extern "C"
     {
     #endif
     #include "foo.h"
     #ifdef __cplusplus
     }  /* end extern "C" */
     #endif

   Calling Fortran code, however, can pose more difficulties.  This is
due to differences in the manner in which compilers treat the linking of
Fortran code with C or C++ code.  Octave supplies several macros that
allow consistent behavior across a number of compilers.

   The underlying Fortran code should use the ‘XSTOPX’ function to
replace the Fortran ‘STOP’ function.  ‘XSTOPX’ uses the Octave exception
handler to treat failing cases in the Fortran code explicitly.  Note
that Octave supplies its own replacement BLAS ‘XERBLA’ function, which
uses ‘XSTOPX’.

   If the code calls ‘XSTOPX’, then the ‘F77_XFCN’ macro should be used
to call the underlying Fortran function.  The Fortran exception state
can then be checked with the global variable
‘f77_exception_encountered’.  If ‘XSTOPX’ will not be called, then the
‘F77_FCN’ macro should be used instead to call the Fortran code.

   There is no great harm in using ‘F77_XFCN’ in all cases, except that
for Fortran code that is short running and executes a large number of
times, there is potentially an overhead in doing so.  However, if
‘F77_FCN’ is used with code that calls ‘XSTOP’, Octave can generate a
segmentation fault.

   An example of the inclusion of a Fortran function in an oct-file is
given in the following example, where the C++ wrapper is

     #include <octave/oct.h>
     #include <octave/f77-fcn.h>
     
     extern "C"
     {
       F77_RET_T
       F77_FUNC (fortransub, FORTSUB)
         (const F77_INT&, F77_DBLE*, F77_CHAR_ARG_DECL F77_CHAR_ARG_LEN_DECL);
     }
     
     DEFUN_DLD (fortrandemo, args, , "Fortran Demo")
     {
       if (args.length () != 1)
         print_usage ();
     
       NDArray a = args(0).array_value ();
     
       double *av = a.fortran_vec ();
       octave_idx_type na = a.numel ();
     
       OCTAVE_LOCAL_BUFFER (char, ctmp, 128);
     
       F77_XFCN (fortransub, FORTSUB,
                 (na, av, ctmp F77_CHAR_ARG_LEN (128)));
     
       return ovl (a, std::string (ctmp));
     }

and the Fortran function is

           subroutine fortransub (n, a, s)
           implicit none
           character*(*) s
           real*8 a(*)
           integer*4 i, n, ioerr
           do i = 1, n
             if (a(i) .eq. 0d0) then
               call xstopx ('fortransub: divide by zero')
             else
               a(i) = 1d0 / a(i)
             endif
           enddo
           write (unit = s, fmt = '(a,i3,a,a)', iostat = ioerr)
          $       'There are ', n,
          $       ' values in the input vector', char(0)
           if (ioerr .ne. 0) then
             call xstopx ('fortransub: error writing string')
           endif
           return
           end

   This example demonstrates most of the features needed to link to an
external Fortran function, including passing arrays and strings, as well
as exception handling.  Both the Fortran and C++ files need to be
compiled in order for the example to work.

     mkoctfile fortrandemo.cc fortransub.f
     [b, s] = fortrandemo (1:3)
     ⇒
       b = 1.00000   0.50000   0.33333
       s = There are   3 values in the input vector
     [b, s] = fortrandemo (0:3)
     error: fortrandemo: fortransub: divide by zero


File: octave.info,  Node: Allocating Local Memory in Oct-Files,  Next: Input Parameter Checking in Oct-Files,  Prev: Calling External Code from Oct-Files,  Up: Oct-Files

A.1.10 Allocating Local Memory in Oct-Files
-------------------------------------------

Allocating memory within an oct-file might seem easy, as the C++
new/delete operators can be used.  However, in that case great care must
be taken to avoid memory leaks.  The preferred manner in which to
allocate memory for use locally is to use the ‘OCTAVE_LOCAL_BUFFER’
macro.  An example of its use is

     OCTAVE_LOCAL_BUFFER (double, tmp, len)

that returns a pointer ‘tmp’ of type ‘double *’ of length ‘len’.

   In this case, Octave itself will worry about reference counting and
variable scope and will properly free memory without programmer
intervention.


File: octave.info,  Node: Input Parameter Checking in Oct-Files,  Next: Exception and Error Handling in Oct-Files,  Prev: Allocating Local Memory in Oct-Files,  Up: Oct-Files

A.1.11 Input Parameter Checking in Oct-Files
--------------------------------------------

Because oct-files are compiled functions they open up the possibility of
crashing Octave through careless function calls or memory faults.  It is
quite important that each and every function have a sufficient level of
parameter checking to ensure that Octave behaves well.

   The minimum requirement, as previously discussed, is to check the
number of input arguments before using them to avoid referencing a
nonexistent argument.  However, in some cases this might not be
sufficient as the underlying code imposes further constraints.  For
example, an external function call might be undefined if the input
arguments are not integers, or if one of the arguments is zero, or if
the input is complex and a real value was expected.  Therefore,
oct-files often need additional input parameter checking.

   There are several functions within Octave that can be useful for the
purposes of parameter checking.  These include the methods of the
‘octave_value’ class like ‘is_real_matrix’, ‘is_numeric_type’, etc.
(see ‘ov.h’).  Often, with a knowledge of the Octave m-file language,
you can guess at what the corresponding C++ routine will.  In addition
there are some more specialized input validation functions of which a
few are demonstrated below.

     #include <octave/oct.h>
     
     DEFUN_DLD (paramdemo, args, nargout, "Parameter Check Demo")
     {
       if (args.length () != 1)
         print_usage ();
     
       NDArray m = args(0).array_value ();
     
       double min_val = -10.0;
       double max_val = 10.0;
     
       octave_stdout << "Properties of input array:\n";
     
       if (m.any_element_is_negative ())
         octave_stdout << "  includes negative values\n";
     
       if (m.any_element_is_inf_or_nan ())
         octave_stdout << "  includes Inf or NaN values\n";
     
       if (m.any_element_not_one_or_zero ())
         octave_stdout << "  includes other values than 1 and 0\n";
     
       if (m.all_elements_are_int_or_inf_or_nan ())
         octave_stdout << "  includes only int, Inf or NaN values\n";
     
       if (m.all_integers (min_val, max_val))
         octave_stdout << "  includes only integers in [-10,10]\n";
     
       return octave_value_list ();
     }

An example of its use is:

     paramdemo ([1, 2, NaN, Inf])
     ⇒ Properties of input array:
          includes Inf or NaN values
          includes other values than 1 and 0
          includes only int, Inf or NaN values


File: octave.info,  Node: Exception and Error Handling in Oct-Files,  Next: Documentation and Testing of Oct-Files,  Prev: Input Parameter Checking in Oct-Files,  Up: Oct-Files

A.1.12 Exception and Error Handling in Oct-Files
------------------------------------------------

Another important feature of Octave is its ability to react to the user
typing <Control-C> during extended calculations.  This ability is based
on the C++ exception handler, where memory allocated by the C++
new/delete methods is automatically released when the exception is
treated.  When writing an oct-file which may run for a long time the
programmer must periodically use the macro ‘OCTAVE_QUIT’, in order to
allow Octave to check and possibly respond to a user typing <Control-C>.
For example:

     for (octave_idx_type i = 0; i < a.nelem (); i++)
       {
         OCTAVE_QUIT;
         b.elem (i) = 2. * a.elem (i);
       }

   The presence of the ‘OCTAVE_QUIT’ macro in the inner loop allows
Octave to detect and acknowledge a <Control-C> key sequence.  Without
this macro, the user must either wait for the oct-file function to
return before the interrupt is processed, or the user must press
<Control-C> three times which will force Octave to exit completely.

   The ‘OCTAVE_QUIT’ macro does impose a very small performance penalty;
For loops that are known to be small it may not make sense to include
‘OCTAVE_QUIT’.

   When creating an oct-file that uses an external library, the function
might spend a significant portion of its time in the external library.
It is not generally possible to use the ‘OCTAVE_QUIT’ macro in this
case.  The alternative code in this case is

     BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
     ...  some code that calls a "foreign" function ...
     END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;

   The disadvantage of this is that if the foreign code allocates any
memory internally, then this memory might be lost during an interrupt,
without being deallocated.  Therefore, ideally Octave itself should
allocate any memory that is needed by the foreign code, with either the
‘fortran_vec’ method or the ‘OCTAVE_LOCAL_BUFFER’ macro.

   The Octave ‘unwind_protect’ mechanism (*note The unwind_protect
Statement::) can also be used in oct-files.  In conjunction with the
exception handling of Octave, it ensures that certain recovery code is
always run even if an exception occurs.  An example of the use of this
mechanism is

     #include <octave/oct.h>
     #include <octave/unwind-prot.h>
     
     void
     my_err_handler (const char *fmt, ...)
     {
       // Do nothing!!
     }
     
     void
     my_err_with_id_handler (const char *id, const char *fmt, ...)
     {
       // Do nothing!!
     }
     
     DEFUN_DLD (unwinddemo, args, nargout, "Unwind Demo")
     {
       if (args.length () < 2)
         print_usage ();
     
       NDArray a = args(0).array_value ();
       NDArray b = args(1).array_value ();
     
       // Declare unwind_protect frame which lasts as long as
       // the variable frame has scope.
       octave::unwind_protect frame;
       frame.add_fcn (set_liboctave_warning_handler,
                      current_liboctave_warning_handler);
     
       frame.add_fcn (set_liboctave_warning_with_id_handler,
                      current_liboctave_warning_with_id_handler);
     
       set_liboctave_warning_handler (my_err_handler);
       set_liboctave_warning_with_id_handler (my_err_with_id_handler);
     
       return octave_value (quotient (a, b));
     }

   As can be seen in the example:

     unwinddemo (1, 0)
     ⇒ Inf
     1 / 0
     ⇒ warning: division by zero
        Inf

   The warning for division by zero (and in fact all warnings) are
disabled in the ‘unwinddemo’ function.


File: octave.info,  Node: Documentation and Testing of Oct-Files,  Prev: Exception and Error Handling in Oct-Files,  Up: Oct-Files

A.1.13 Documentation and Testing of Oct-Files
---------------------------------------------

The documentation for an oct-file is contained in the fourth string
parameter of the ‘DEFUN_DLD’ macro.  This string can be formatted in the
same manner as the help strings for user functions, however there are
some issues that are particular to the formatting of help strings within
oct-files.

   The major issue is that the help string will typically be longer than
a single line of text, and so the formatting of long multi-line help
strings needs to be taken into account.  There are several possible
solutions, but the most common is illustrated in the following example,

     DEFUN_DLD (do_what_i_want, args, nargout,
       "-*- texinfo -*-\n\
     @deftypefn {} {} do_what_i_say (@var{n})\n\
     A function that does what the user actually wants rather\n\
     than what they requested.\n\
     @end deftypefn")
     {
     ...
     }

where each line of text is terminated by ‘\n\’ which is an embedded
newline in the string together with a C++ string continuation character.
Note that the final ‘\’ must be the last character on the line.

   Octave also includes the ability to embed test and demonstration code
for a function within the code itself (*note Test and Demo Functions::).
This can be used from within oct-files (or in fact any file) with
certain provisos.  First, the test and demo functions of Octave look for
‘%!’ as the first two characters of a line to identify test and
demonstration code.  This is a requirement for oct-files as well.  In
addition, the test and demonstration code must be wrapped in a comment
block to avoid it being interpreted by the compiler.  Finally, the
Octave test and demonstration code must have access to the original
source code of the oct-file—not just the compiled code—as the tests are
stripped from the compiled code.  An example in an oct-file might be

     /*
     %!assert (sin ([1,2]), [sin(1),sin(2)])
     %!error (sin ())
     %!error (sin (1,1))
     */


File: octave.info,  Node: Mex-Files,  Next: Standalone Programs,  Prev: Oct-Files,  Up: External Code Interface

A.2 Mex-Files
=============

Octave includes an interface to allow legacy mex-files to be compiled
and used with Octave.  This interface can also be used to share compiled
code between Octave and MATLAB users.  However, as mex-files expose
MATLAB’s internal API, and the internal structure of Octave is
different, a mex-file can never have the same performance in Octave as
the equivalent oct-file.  In particular, to support the manner in which
variables are passed to mex functions there are a significant number of
additional copies of memory blocks when invoking or returning from a
mex-file function.  For this reason, it is recommended that any new code
be written with the oct-file interface previously discussed.

* Menu:

* Getting Started with Mex-Files::
* Working with Matrices and Arrays in Mex-Files::
* Character Strings in Mex-Files::
* Cell Arrays with Mex-Files::
* Structures with Mex-Files::
* Sparse Matrices with Mex-Files::
* Calling Other Functions in Mex-Files::


File: octave.info,  Node: Getting Started with Mex-Files,  Next: Working with Matrices and Arrays in Mex-Files,  Up: Mex-Files

A.2.1 Getting Started with Mex-Files
------------------------------------

The basic command to build a mex-file is either ‘mkoctfile --mex’ or
‘mex’.  The first command can be used either from within Octave or from
the command line.  To avoid issues with MATLAB’s own ‘mex’ command, the
use of the command ‘mex’ is limited to within Octave.  Compiled
mex-files have the extension ‘.mex’.

 -- : mex [options] file ...
     Compile source code written in C, C++, or Fortran, to a MEX file.

     This is equivalent to ‘mkoctfile --mex [options] file’.

     See also: *note mkoctfile: XREFmkoctfile, *note mexext: XREFmexext.

 -- : mexext ()
     Return the filename extension used for MEX files.

     See also: *note mex: XREFmex.

   Consider the following short example:

     #include "mex.h"
     
     void
     mexFunction (int nlhs, mxArray *plhs[],
                  int nrhs, const mxArray *prhs[])
     {
       mexPrintf ("Hello, World!\n");
     
       mexPrintf ("I have %d inputs and %d outputs\n", nrhs, nlhs);
     
       /* Return empty matrices for any outputs */
       int i;
       for (i = 0; i < nlhs; i++)
         plhs[i] = mxCreateDoubleMatrix (0, 0, mxREAL);
     }

   The first line ‘#include "mex.h"’ makes available all of the
definitions necessary for a mex-file.  One important difference between
Octave and MATLAB is that the header file "matrix.h" is implicitly
included through the inclusion of "mex.h".  This is necessary to avoid a
conflict with the Octave file "Matrix.h" for operating systems and
compilers that don’t distinguish between filenames in upper and lower
case.

   The entry point into the mex-file is defined by ‘mexFunction’.  The
function takes four arguments:

  1. The number of return arguments (# of left-hand side args).

  2. An array of pointers to return arguments.

  3. The number of input arguments (# of right-hand side args).

  4. An array of pointers to input arguments.

   Note that the function name definition is not explicitly included in
‘mexFunction’ and so there can only be a single ‘mexFunction’ entry
point per file.  Instead, the name of the function as seen in Octave is
determined by the name of the mex-file itself minus the extension.  If
the above function is in the file ‘myhello.c’, it can be compiled with

     mkoctfile --mex myhello.c

which creates a file ‘myhello.mex’.  The function can then be run from
Octave as

     myhello (1,2,3)
     ⇒ Hello, World!
     ⇒ I have 3 inputs and 0 outputs

   It should be noted that the mex-file contains no help string.  To
document mex-files, there should exist an m-file in the same directory
as the mex-file itself.  Taking the above as an example, there would
need to be a file ‘myhello.m’ which might contain the text

     %MYHELLO Simple test of the functionality of a mex-file.

   In this case, the function that will be executed within Octave will
be given by the mex-file, while the help string will come from the
m-file.  This can also be useful to allow a sample implementation of the
mex-file within the Octave language itself for testing purposes.

   Although there cannot be multiple entry points in a single mex-file,
one can use the ‘mexFunctionName’ function to determine what name the
mex-file was called with.  This can be used to alter the behavior of the
mex-file based on the function name.  For example, if

     #include "mex.h"
     
     void
     mexFunction (int nlhs, mxArray *plhs[],
                  int nrhs, const mxArray *prhs[])
     {
       const char *nm;
     
       nm = mexFunctionName ();
       mexPrintf ("You called function: %s\n", nm);
       if (strcmp (nm, "myfunc") == 0)
         mexPrintf ("This is the principal function\n", nm);
     
       return;
     }

is in the file ‘myfunc.c’, and is compiled with

     mkoctfile --mex myfunc.c
     ln -s myfunc.mex myfunc2.mex

then as can be seen by

     myfunc ()
     ⇒ You called function: myfunc
         This is the principal function
     myfunc2 ()
     ⇒ You called function: myfunc2

the behavior of the mex-file can be altered depending on the function’s
name.

   Although the user should only include ‘mex.h’ in their code, Octave
declares additional functions, typedefs, etc., available to the user to
write mex-files in the headers ‘mexproto.h’ and ‘mxarray.h’.


File: octave.info,  Node: Working with Matrices and Arrays in Mex-Files,  Next: Character Strings in Mex-Files,  Prev: Getting Started with Mex-Files,  Up: Mex-Files

A.2.2 Working with Matrices and Arrays in Mex-Files
---------------------------------------------------

The basic mex type of all variables is ‘mxArray’.  Any object, such as a
matrix, cell array, or structure, is stored in this basic type.
‘mxArray’ serves essentially the same purpose as the ‘octave_value’
class in oct-files in that it acts as a container for all the more
specialized types.

   The ‘mxArray’ structure contains at a minimum, the name of the
variable it represents, its dimensions, its type, and whether the
variable is real or complex.  It can also contain a number of additional
fields depending on the type of the ‘mxArray’.  There are a number of
functions to create ‘mxArray’ structures, including
‘mxCreateDoubleMatrix’, ‘mxCreateCellArray’, ‘mxCreateSparse’, and the
generic ‘mxCreateNumericArray’.

   The basic function to access the data in an array is ‘mxGetPr’.
Because the mex interface assumes that real and imaginary parts of a
complex array are stored separately, there is an equivalent function
‘mxGetPi’ that gets the imaginary part.  Both of these functions are
only for use with double precision matrices.  The generic functions
‘mxGetData’ and ‘mxGetImagData’ perform the same operation for all
matrix types.  For example:

     mxArray *m;
     mwSize *dims;
     UINT32_T *pr;

     dims = (mwSize *) mxMalloc (2 * sizeof (mwSize));
     dims[0] = 2; dims[1] = 2;
     m = mxCreateNumericArray (2, dims, mxUINT32_CLASS, mxREAL);
     pr = (UINT32_T *) mxGetData (m);

   There are also the functions ‘mxSetPr’, etc., that perform the
inverse, and set the data of an array to use the block of memory pointed
to by the argument of ‘mxSetPr’.

   Note the type ‘mwSize’ used above, and also ‘mwIndex’, are defined as
the native precision of the indexing in Octave on the platform on which
the mex-file is built.  This allows both 32- and 64-bit platforms to
support mex-files.  ‘mwSize’ is used to define array dimensions and the
maximum number or elements, while ‘mwIndex’ is used to define indexing
into arrays.

   An example that demonstrates how to work with arbitrary real or
complex double precision arrays is given by the file ‘mypow2.c’ shown
below.

     #include "mex.h"
     
     void
     mexFunction (int nlhs, mxArray *plhs[],
                  int nrhs, const mxArray *prhs[])
     {
       mwSize n;
       mwIndex i;
       double *vri, *vro;
     
       if (nrhs != 1 || ! mxIsDouble (prhs[0]))
         mexErrMsgTxt ("ARG1 must be a double matrix");
     
       n = mxGetNumberOfElements (prhs[0]);
       plhs[0] = mxCreateNumericArray (mxGetNumberOfDimensions (prhs[0]),
                                       mxGetDimensions (prhs[0]),
                                       mxGetClassID (prhs[0]),
                                       mxIsComplex (prhs[0]));
       vri = mxGetPr (prhs[0]);
       vro = mxGetPr (plhs[0]);
     
       if (mxIsComplex (prhs[0]))
         {
           double *vii, *vio;
           vii = mxGetPi (prhs[0]);
           vio = mxGetPi (plhs[0]);
     
           for (i = 0; i < n; i++)
             {
               vro[i] = vri[i] * vri[i] - vii[i] * vii[i];
               vio[i] = 2 * vri[i] * vii[i];
             }
         }
       else
         {
           for (i = 0; i < n; i++)
             vro[i] = vri[i] * vri[i];
         }
     }

An example of its use is

     b = randn (4,1) + 1i * randn (4,1);
     all (b.^2 == mypow2 (b))
     ⇒ 1

   The example above uses the functions ‘mxGetDimensions’,
‘mxGetNumberOfElements’, and ‘mxGetNumberOfDimensions’ to work with the
dimensions of multi-dimensional arrays.  The functions ‘mxGetM’, and
‘mxGetN’ are also available to find the number of rows and columns in a
2-D matrix (MxN matrix).


File: octave.info,  Node: Character Strings in Mex-Files,  Next: Cell Arrays with Mex-Files,  Prev: Working with Matrices and Arrays in Mex-Files,  Up: Mex-Files

A.2.3 Character Strings in Mex-Files
------------------------------------

As mex-files do not make the distinction between single and double
quoted strings that Octave does, there is perhaps less complexity in the
use of strings and character matrices.  An example of their use that
parallels the demo in ‘stringdemo.cc’ is given in the file ‘mystring.c’,
as shown below.

     #include <string.h>
     #include "mex.h"
     
     void
     mexFunction (int nlhs, mxArray *plhs[],
                  int nrhs, const mxArray *prhs[])
     {
       mwSize m, n;
       mwIndex i, j;
       mxChar *pi, *po;
     
       if (nrhs != 1 || ! mxIsChar (prhs[0])
           || mxGetNumberOfDimensions (prhs[0]) > 2)
         mexErrMsgTxt ("ARG1 must be a char matrix");
     
       m = mxGetM (prhs[0]);
       n = mxGetN (prhs[0]);
       pi = mxGetChars (prhs[0]);
       plhs[0] = mxCreateNumericMatrix (m, n, mxCHAR_CLASS, mxREAL);
       po = mxGetChars (plhs[0]);
     
       for (j = 0; j < n; j++)
         for (i = 0; i < m; i++)
           po[j*m + m - 1 - i] = pi[j*m + i];
     }

An example of its expected output is

     mystring (["First String"; "Second String"])
     ⇒ Second String
        First String

   Other functions in the mex interface for handling character strings
are ‘mxCreateString’, ‘mxArrayToString’, and
‘mxCreateCharMatrixFromStrings’.  In a mex-file, a character string is
considered to be a vector rather than a matrix.  This is perhaps an
arbitrary distinction as the data in the ‘mxArray’ for the matrix is
consecutive in any case.


File: octave.info,  Node: Cell Arrays with Mex-Files,  Next: Structures with Mex-Files,  Prev: Character Strings in Mex-Files,  Up: Mex-Files

A.2.4 Cell Arrays with Mex-Files
--------------------------------

One can perform exactly the same operations on Cell arrays in mex-files
as in oct-files.  An example that duplicates the function of the
‘celldemo.cc’ oct-file in a mex-file is given by ‘mycell.c’ as shown
below.

     #include "mex.h"
     
     void
     mexFunction (int nlhs, mxArray *plhs[],
                  int nrhs, const mxArray *prhs[])
     {
       mwSize n;
       mwIndex i;
     
       if (nrhs != 1 || ! mxIsCell (prhs[0]))
         mexErrMsgTxt ("ARG1 must be a cell");
     
       n = mxGetNumberOfElements (prhs[0]);
       n = (n > nlhs ? nlhs : n);
     
       for (i = 0; i < n; i++)
         plhs[i] = mxDuplicateArray (mxGetCell (prhs[0], i));
     }

The output is identical to the oct-file version as well.

     [b1, b2, b3] = mycell ({1, [1, 2], "test"})
     ⇒
     b1 =  1
     b2 =

        1   2

     b3 = test

   Note in the example the use of the ‘mxDuplicateArray’ function.  This
is needed as the ‘mxArray’ pointer returned by ‘mxGetCell’ might be
deallocated.  The inverse function to ‘mxGetCell’, used for setting Cell
values, is ‘mxSetCell’ and is defined as

     void mxSetCell (mxArray *ptr, int idx, mxArray *val);

   Finally, to create a cell array or matrix, the appropriate functions
are

     mxArray *mxCreateCellArray (int ndims, const int *dims);
     mxArray *mxCreateCellMatrix (int m, int n);


File: octave.info,  Node: Structures with Mex-Files,  Next: Sparse Matrices with Mex-Files,  Prev: Cell Arrays with Mex-Files,  Up: Mex-Files

A.2.5 Structures with Mex-Files
-------------------------------

The basic function to create a structure in a mex-file is
‘mxCreateStructMatrix’ which creates a structure array with a two
dimensional matrix, or ‘mxCreateStructArray’.

     mxArray *mxCreateStructArray (int ndims, int *dims,
                                   int num_keys,
                                   const char **keys);
     mxArray *mxCreateStructMatrix (int rows, int cols,
                                    int num_keys,
                                    const char **keys);

   Accessing the fields of the structure can then be performed with
‘mxGetField’ and ‘mxSetField’ or alternatively with the
‘mxGetFieldByNumber’ and ‘mxSetFieldByNumber’ functions.

     mxArray *mxGetField (const mxArray *ptr, mwIndex index,
                          const char *key);
     mxArray *mxGetFieldByNumber (const mxArray *ptr,
                                  mwIndex index, int key_num);
     void mxSetField (mxArray *ptr, mwIndex index,
                      const char *key, mxArray *val);
     void mxSetFieldByNumber (mxArray *ptr, mwIndex index,
                              int key_num, mxArray *val);

   A difference between the oct-file interface to structures and the
mex-file version is that the functions to operate on structures in
mex-files directly include an ‘index’ over the elements of the arrays of
elements per ‘field’; Whereas, the oct-file structure includes a Cell
Array per field of the structure.

   An example that demonstrates the use of structures in a mex-file can
be found in the file ‘mystruct.c’ shown below.

     #include "mex.h"
     
     void
     mexFunction (int nlhs, mxArray *plhs[],
                  int nrhs, const mxArray *prhs[])
     {
       int i;
       mwIndex j;
       mxArray *v;
       const char *keys[] = { "this", "that" };
     
       if (nrhs != 1 || ! mxIsStruct (prhs[0]))
         mexErrMsgTxt ("ARG1 must be a struct");
     
       for (i = 0; i < mxGetNumberOfFields (prhs[0]); i++)
         for (j = 0; j < mxGetNumberOfElements (prhs[0]); j++)
           {
             mexPrintf ("field %s(%d) = ", mxGetFieldNameByNumber (prhs[0], i), j);
             v = mxGetFieldByNumber (prhs[0], j, i);
             mexCallMATLAB (0, NULL, 1, &v, "disp");
           }
     
       v = mxCreateStructMatrix (2, 2, 2, keys);
     
       mxSetFieldByNumber (v, 0, 0, mxCreateString ("this1"));
       mxSetFieldByNumber (v, 0, 1, mxCreateString ("that1"));
       mxSetFieldByNumber (v, 1, 0, mxCreateString ("this2"));
       mxSetFieldByNumber (v, 1, 1, mxCreateString ("that2"));
       mxSetFieldByNumber (v, 2, 0, mxCreateString ("this3"));
       mxSetFieldByNumber (v, 2, 1, mxCreateString ("that3"));
       mxSetFieldByNumber (v, 3, 0, mxCreateString ("this4"));
       mxSetFieldByNumber (v, 3, 1, mxCreateString ("that4"));
     
       if (nlhs)
         plhs[0] = v;
     }

   An example of the behavior of this function within Octave is then

     a(1).f1 = "f11"; a(1).f2 = "f12";
     a(2).f1 = "f21"; a(2).f2 = "f22";
     b = mystruct (a);
     ⇒  field f1(0) = f11
         field f1(1) = f21
         field f2(0) = f12
         field f2(1) = f22
     b
     ⇒ 2x2 struct array containing the fields:

          this
          that

     b(3)
     ⇒ scalar structure containing the fields:

          this = this3
          that = that3


File: octave.info,  Node: Sparse Matrices with Mex-Files,  Next: Calling Other Functions in Mex-Files,  Prev: Structures with Mex-Files,  Up: Mex-Files

A.2.6 Sparse Matrices with Mex-Files
------------------------------------

The Octave format for sparse matrices is identical to the mex format in
that it is a compressed column sparse format.  Also, in both
implementations sparse matrices are required to be two-dimensional.  The
only difference of importance to the programmer is that the real and
imaginary parts of the matrix are stored separately.

   The mex-file interface, in addition to using ‘mxGetM’, ‘mxGetN’,
‘mxSetM’, ‘mxSetN’, ‘mxGetPr’, ‘mxGetPi’, ‘mxSetPr’, and ‘mxSetPi’, also
supplies the following functions.

     mwIndex *mxGetIr (const mxArray *ptr);
     mwIndex *mxGetJc (const mxArray *ptr);
     mwSize mxGetNzmax (const mxArray *ptr);

     void mxSetIr (mxArray *ptr, mwIndex *ir);
     void mxSetJc (mxArray *ptr, mwIndex *jc);
     void mxSetNzmax (mxArray *ptr, mwSize nzmax);

‘mxGetNzmax’ gets the maximum number of elements that can be stored in
the sparse matrix.  This is not necessarily the number of nonzero
elements in the sparse matrix.  ‘mxGetJc’ returns an array with one
additional value than the number of columns in the sparse matrix.  The
difference between consecutive values of the array returned by ‘mxGetJc’
define the number of nonzero elements in each column of the sparse
matrix.  Therefore,

     mwSize nz, n;
     mwIndex *Jc;
     mxArray *m;
     ...
     n = mxGetN (m);
     Jc = mxGetJc (m);
     nz = Jc[n];

returns the actual number of nonzero elements stored in the matrix in
‘nz’.  As the arrays returned by ‘mxGetPr’ and ‘mxGetPi’ only contain
the nonzero values of the matrix, we also need a pointer to the rows of
the nonzero elements, and this is given by ‘mxGetIr’.  A complete
example of the use of sparse matrices in mex-files is given by the file
‘mysparse.c’ shown below.

     #include "mex.h"
     
     void
     mexFunction (int nlhs, mxArray *plhs[],
                  int nrhs, const mxArray *prhs[])
     {
       mwSize m, n, nz;
       mxArray *v;
       mwIndex i;
       double *pr, *pi;
       double *pr2, *pi2;
       mwIndex *ir, *jc;
       mwIndex *ir2, *jc2;
     
       if (nrhs != 1 || ! mxIsSparse (prhs[0]))
         mexErrMsgTxt ("ARG1 must be a sparse matrix");
     
       m = mxGetM (prhs[0]);
       n = mxGetN (prhs[0]);
       nz = mxGetNzmax (prhs[0]);
     
       if (mxIsComplex (prhs[0]))
         {
           mexPrintf ("Matrix is %d-by-%d complex sparse matrix", m, n);
           mexPrintf (" with %d elements\n", nz);
     
           pr = mxGetPr (prhs[0]);
           pi = mxGetPi (prhs[0]);
           ir = mxGetIr (prhs[0]);
           jc = mxGetJc (prhs[0]);
     
           i = n;
           while (jc[i] == jc[i-1] && i != 0) i--;
     
           mexPrintf ("last nonzero element (%d, %d) = (%g, %g)\n",
                      ir[nz-1]+ 1, i, pr[nz-1], pi[nz-1]);
     
           v = mxCreateSparse (m, n, nz, mxCOMPLEX);
           pr2 = mxGetPr (v);
           pi2 = mxGetPi (v);
           ir2 = mxGetIr (v);
           jc2 = mxGetJc (v);
     
           for (i = 0; i < nz; i++)
             {
               pr2[i] = 2 * pr[i];
               pi2[i] = 2 * pi[i];
               ir2[i] = ir[i];
             }
           for (i = 0; i < n + 1; i++)
             jc2[i] = jc[i];
     
           if (nlhs > 0)
             plhs[0] = v;
         }
       else if (mxIsLogical (prhs[0]))
         {
           mxLogical *pbr, *pbr2;
           mexPrintf ("Matrix is %d-by-%d logical sparse matrix", m, n);
           mexPrintf (" with %d elements\n", nz);
     
           pbr = mxGetLogicals (prhs[0]);
           ir = mxGetIr (prhs[0]);
           jc = mxGetJc (prhs[0]);
     
           i = n;
           while (jc[i] == jc[i-1] && i != 0) i--;
           mexPrintf ("last nonzero element (%d, %d) = %d\n",
                      ir[nz-1]+ 1, i, pbr[nz-1]);
     
           v = mxCreateSparseLogicalMatrix (m, n, nz);
           pbr2 = mxGetLogicals (v);
           ir2 = mxGetIr (v);
           jc2 = mxGetJc (v);
     
           for (i = 0; i < nz; i++)
             {
               pbr2[i] = pbr[i];
               ir2[i] = ir[i];
             }
           for (i = 0; i < n + 1; i++)
             jc2[i] = jc[i];
     
           if (nlhs > 0)
             plhs[0] = v;
         }
       else
         {
           mexPrintf ("Matrix is %d-by-%d real sparse matrix", m, n);
           mexPrintf (" with %d elements\n", nz);
     
           pr = mxGetPr (prhs[0]);
           ir = mxGetIr (prhs[0]);
           jc = mxGetJc (prhs[0]);
     
           i = n;
           while (jc[i] == jc[i-1] && i != 0) i--;
           mexPrintf ("last nonzero element (%d, %d) = %g\n",
                      ir[nz-1]+ 1, i, pr[nz-1]);
     
           v = mxCreateSparse (m, n, nz, mxREAL);
           pr2 = mxGetPr (v);
           ir2 = mxGetIr (v);
           jc2 = mxGetJc (v);
     
           for (i = 0; i < nz; i++)
             {
               pr2[i] = 2 * pr[i];
               ir2[i] = ir[i];
             }
           for (i = 0; i < n + 1; i++)
             jc2[i] = jc[i];
     
           if (nlhs > 0)
             plhs[0] = v;
         }
     }

   A sample usage of ‘mysparse’ is

     sm = sparse ([1, 0; 0, pi]);
     mysparse (sm)
     ⇒
     Matrix is 2-by-2 real sparse matrix with 2 elements
     last nonzero element (2, 2) = 3.14159


File: octave.info,  Node: Calling Other Functions in Mex-Files,  Prev: Sparse Matrices with Mex-Files,  Up: Mex-Files

A.2.7 Calling Other Functions in Mex-Files
------------------------------------------

It is possible to call other Octave functions from within a mex-file
using ‘mexCallMATLAB’.  An example of the use of ‘mexCallMATLAB’ can be
see in the example below.

     #include "mex.h"
     
     void
     mexFunction (int nlhs, mxArray *plhs[],
                  int nrhs, const mxArray *prhs[])
     {
       char *str;
     
       mexPrintf ("Starting file myfeval.mex\n");
     
       mexPrintf ("I have %d inputs and %d outputs\n", nrhs, nlhs);
     
       if (nrhs < 1 || ! mxIsChar (prhs[0]))
         mexErrMsgTxt ("ARG1 must be a function name");
     
       str = mxArrayToString (prhs[0]);
     
       mexPrintf ("I'm going to call the function %s\n", str);
     
       if (nlhs == 0)
         nlhs = 1;  // Octave's automatic 'ans' variable
     
       /* Cast prhs just to get rid of 'const' qualifier and stop compile warning */
       mexCallMATLAB (nlhs, plhs, nrhs-1, (mxArray**)prhs+1, str);
     
       mxFree (str);
     }

   If this code is in the file ‘myfeval.c’, and is compiled to
‘myfeval.mex’, then an example of its use is

     a = myfeval ("sin", 1)
     ⇒ Starting file myfeval.mex
        I have 2 inputs and 1 outputs
        I'm going to call the interpreter function sin
        a =  0.84147

   Note that it is not possible to use function handles or inline
functions within a mex-file.


File: octave.info,  Node: Standalone Programs,  Next: Java Interface,  Prev: Mex-Files,  Up: External Code Interface

A.3 Standalone Programs
=======================

The libraries Octave uses itself can be utilized in standalone
applications.  These applications then have access, for example, to the
array and matrix classes, as well as to all of the Octave algorithms.
The following C++ program, uses class Matrix from ‘liboctave.a’ or
‘liboctave.so’.

     #include <iostream>
     #include <octave/oct.h>
     
     int
     main (void)
     {
       std::cout << "Hello Octave world!\n";
     
       int n = 2;
       Matrix a_matrix = Matrix (n, n);
     
       for (octave_idx_type i = 0; i < n; i++)
         for (octave_idx_type j = 0; j < n; j++)
           a_matrix(i,j) = (i + 1) * 10 + (j + 1);
     
       std::cout << a_matrix;
     
       return 0;
     }

mkoctfile can be used to build a standalone application with a command
like

     $ mkoctfile --link-stand-alone standalone.cc -o standalone
     $ ./standalone
     Hello Octave world!
       11 12
       21 22
     $

   Note that the application ‘standalone’ will be dynamically linked
against the Octave libraries and any Octave support libraries.  The
above allows the Octave math libraries to be used by an application.  It
does not, however, allow the script files, oct-files, or built-in
functions of Octave to be used by the application.  To do that, the
Octave interpreter needs to be initialized first.  An example of how to
do this can then be seen in the code

     #include <iostream>
     #include <octave/oct.h>
     #include <octave/octave.h>
     #include <octave/parse.h>
     #include <octave/interpreter.h>
     
     int
     main (void)
     {
       // Create interpreter.
     
       octave::interpreter interpreter;
     
       try
         {
           // Inhibit reading history file by calling
           //
           //   interpreter.initialize_history (false);
     
           // Set custom load path here if you wish by calling
           //
           //   interpreter.initialize_load_path (false);
     
           // Perform final initialization of interpreter, including
           // executing commands from startup files by calling
           //
           //   int status interpreter.initialize ();
           //
           //   if (! interpreter.initialized ())
           //     {
           //       std::cerr << "Octave interpreter initialization failed!"
           //                 << std::endl;
           //       exit (status);
           //     }
           //
           // You may skip this step if you don't need to do anything
           // between reading the startup files and telling the interpreter
           // that you are ready to execute commands.
     
           // Tell the interpreter that we're ready to execute commands:
     
           int status = interpreter.execute ();
     
           if (status != 0)
             {
               std::cerr << "creating embedded Octave interpreter failed!"
                         << std::endl;
               return status;
             }
     
           octave_idx_type n = 2;
           octave_value_list in;
     
           for (octave_idx_type i = 0; i < n; i++)
             in(i) = octave_value (5 * (i + 2));
     
           octave_value_list out = octave::feval ("gcd", in, 1);
     
           if (out.length () > 0)
             std::cout << "GCD of ["
                       << in(0).int_value ()
                       << ", "
                       << in(1).int_value ()
                       << "] is " << out(0).int_value ()
                       << std::endl;
           else
             std::cout << "invalid\n";
         }
       catch (const octave::exit_exception& ex)
         {
           std::cerr << "Octave interpreter exited with status = "
                     << ex.exit_status () << std::endl;
         }
       catch (const octave::execution_exception&)
         {
           std::cerr << "error encountered in Octave evaluator!" << std::endl;
         }
     
       return 0;
     }

which, as before, is compiled and run as a standalone application with

     $ mkoctfile --link-stand-alone embedded.cc -o embedded
     $ ./embedded
     GCD of [10, 15] is 5
     $

   It is worth re-iterating that, if only built-in functions are to be
called from a C++ standalone program then it does not need to initialize
the interpreter.  The general rule is that for a built-in function named
‘function_name’ in the interpreter, there will be a C++ function named
‘Ffunction_name’ (note the prepended capital ‘F’) accessible in the C++
API.  The declarations for all built-in functions are collected in the
header file ‘builtin-defun-decls.h’.  This feature should be used with
care as the list of built-in functions can change.  No guarantees can be
made that a function that is currently a built-in won’t be implemented
as a .m file or as a dynamically linked function in the future.  An
example of how to call built-in functions from C++ can be seen in the
code

     #include <iostream>
     #include <octave/oct.h>
     #include <octave/builtin-defun-decls.h>
     
     int
     main (void)
     {
       int n = 2;
       Matrix a_matrix = Matrix (n, n);
     
       for (octave_idx_type i = 0; i < n; i++)
         for (octave_idx_type j = 0; j < n; j++)
           a_matrix(i,j) = (i + 1) * 10 + (j + 1);
     
       std::cout << "This is a matrix:" << std::endl
                 << a_matrix            << std::endl;
     
       octave_value_list in;
       in(0) = a_matrix;
     
       octave_value_list out = Fnorm (in, 1);
       double norm_of_the_matrix = out(0).double_value ();
     
       std::cout << "This is the norm of the matrix:" << std::endl
                 << norm_of_the_matrix                << std::endl;
     
       return 0;
     }

which is compiled and run as a standalone application with

     $ mkoctfile --link-stand-alone standalonebuiltin.cc -o standalonebuiltin
     $ ./standalonebuiltin
     This is a matrix:
      11 12
      21 22

     This is the norm of the matrix:
     34.4952
     $


File: octave.info,  Node: Java Interface,  Prev: Standalone Programs,  Up: External Code Interface

A.4 Java Interface
==================

The Java Interface is designed for calling Java functions from within
Octave.  If you want to do the reverse, and call Octave from within
Java, try a library like ‘joPas’ (<http://jopas.sourceforge.net>).

* Menu:

* Making Java Classes Available::
* How to use Java from within Octave::
* Set up the JVM::
* Java Interface Functions::


File: octave.info,  Node: Making Java Classes Available,  Next: How to use Java from within Octave,  Up: Java Interface

A.4.1 Making Java Classes Available
-----------------------------------

Java finds classes by searching a CLASSPATH which is a list of Java
archive files and/or directories containing class files.  In Octave the
CLASSPATH is composed of two parts:

   • the STATIC CLASSPATH is initialized once at startup of the JVM, and

   • the DYNAMIC CLASSPATH which can be modified at runtime.

   Octave searches the STATIC CLASSPATH first, and then the DYNAMIC
CLASSPATH.  Classes appearing in the STATIC CLASSPATH, as well as in the
DYNAMIC CLASSPATH, will therefore be found in the STATIC CLASSPATH and
loaded from this location.  Classes which will be used frequently, or
must be available to all users, should be added to the STATIC CLASSPATH.
The STATIC CLASSPATH is populated once from the contents of a plain text
file named ‘javaclasspath.txt’ (or ‘classpath.txt’ historically) when
the Java Virtual Machine starts.  This file contains one line for each
individual classpath to be added to the STATIC CLASSPATH.  These lines
can identify directories containing class files, or Java archives with
complete class file hierarchies.  Comment lines starting with a ‘#’ or a
‘%’ character are ignored.

   The search rules for the file ‘javaclasspath.txt’ (or
‘classpath.txt’) are:

   • First, Octave tries to locate it in the current directory (where
     Octave was started from).  If such a file is found, it is read and
     defines the initial STATIC CLASSPATH.  Thus, it is possible to
     define a static classpath on a ’per Octave invocation’ basis.

   • Next, Octave searches in the user’s home directory.  If a file
     ‘javaclasspath.txt’ exists here, its contents are appended to the
     static classpath (if any).  Thus, it is possible to build an
     initial static classpath on a ’per user’ basis.

   • Finally, Octave looks for a ‘javaclasspath.txt’ in the m-file
     directory where Octave Java functions live.  This is where the
     function ‘javaclasspath.m’ resides, usually something like
     ‘OCTAVE_HOME/share/octave/OCTAVE_VERSION/m/java/’.  You can find
     this directory by executing the command

          which javaclasspath

     If this file exists here, its contents are also appended to the
     STATIC CLASSPATH.  Note that the archives and class directories
     defined in this last step will affect all users.

   Classes which are used only by a specific script should be placed in
the DYNAMIC CLASSPATH.  This portion of the classpath can be modified at
runtime using the ‘javaaddpath’ and ‘javarmpath’ functions.

   Example:

     octave> base_path = "C:/Octave/java_files";

     octave> # add two JAR archives to the dynamic classpath
     octave> javaaddpath ([base_path, "/someclasses.jar"]);
     octave> javaaddpath ([base_path, "/moreclasses.jar"]);

     octave> # check the dynamic classpath
     octave> p = javaclasspath;
     octave> disp (p{1});
     C:/Octave/java_files/someclasses.jar
     octave> disp (p{2});
     C:/Octave/java_files/moreclasses.jar

     octave> # remove the first element from the classpath
     octave> javarmpath ([base_path, "/someclasses.jar"]);
     octave> p = javaclasspath;
     octave> disp (p{1});
     C:/Octave/java_files/moreclasses.jar

     octave> # provoke an error
     octave> disp (p{2});
     error: A(I): Index exceeds matrix dimension.

   Another way to add files to the DYNAMIC CLASSPATH exclusively for
your user account is to use the file ‘.octaverc’ which is stored in your
home directory.  All Octave commands in this file are executed each time
you start a new instance of Octave.  The following example adds the
directory ‘octave’ to Octave’s search path and the archive
‘myclasses.jar’ in this directory to the Java search path.

     # contents of .octaverc:
     addpath ("~/octave");
     javaaddpath ("~/octave/myclasses.jar");


File: octave.info,  Node: How to use Java from within Octave,  Next: Set up the JVM,  Prev: Making Java Classes Available,  Up: Java Interface

A.4.2 How to use Java from within Octave
----------------------------------------

The function *note javaObject: XREFjavaObject. creates Java objects.  In
fact it invokes the public constructor of the class with the given name
and with the given parameters.

   The following example shows how to invoke the constructors
‘BigDecimal(double)’ and ‘BigDecimal(String)’ of the builtin Java class
‘java.math.BigDecimal’.

     javaObject ("java.math.BigDecimal",  1.001 );
     javaObject ("java.math.BigDecimal", "1.001");

   Note that parameters of the Octave type ‘double’ are implicitly
converted into the Java type ‘double’ and the Octave type (array of)
‘char’ is converted into the java type ‘String’.  A Java object created
by *note javaObject: XREFjavaObject. is never automatically converted
into an Octave type but remains a Java object.  It can be assigned to an
Octave variable.

     a = 1.001;
     b = javaObject ("java.math.BigDecimal", a);

   Using *note isjava: XREFisjava, it is possible to check whether a
variable is a Java object and its class can be determined as well.  In
addition to the previous example:

     isjava (a)
     ⇒ ans = 0
     class (a)
     ⇒ ans = double
     isjava (b)
     ⇒ ans = 1
     class (b)
     ⇒ ans = java.math.BigDecimal

   The example above can be carried out using only Java objects:

     a = javaObject ("java.lang.Double", 1.001);
     b = javaObject ("java.math.BigDecimal", a);

     isjava (a)
     ⇒ ans = 1
     class (a)
     ⇒ ans = java.lang.Double
     isjava (b)
     ⇒ ans = 1
     class (b)
     ⇒ ans = java.math.BigDecimal

   One can see, that even a ‘java.lang.Double’ is not converted to an
Octave ‘double’, when created by *note javaObject: XREFjavaObject.  But
ambiguities might arise, if the Java classes ‘java.lang.Double’ or
‘double’ are parameters of a method (or a constructor).  In this case
they can be converted into one another, depending on the context.

   Via *note javaObject: XREFjavaObject. one may create all kinds of
Java objects but arrays.  The latter are created through *note
javaArray: XREFjavaArray.

   It is possible to invoke public member methods on Java objects in
Java syntax:

     a.toString
     ⇒ ans = 1.001
     b.toString
     ⇒ ans = 1.000999999999999889865...

   The second result may be surprising, but simply comes from the fact,
that ‘1.001’ cannot exactly be represented as ‘double’, due to rounding.
Note that unlike in Java, in Octave methods without arguments can be
invoked with and without parentheses ‘()’.

   Currently it is not possible to invoke static methods with a Java
like syntax from within Octave.  Instead, one has to use the function
*note javaMethod: XREFjavaMethod. as in the following example:

     java.math.BigDecimal.valueOf(1.001);                    # does not work
     javaMethod ("valueOf", "java.math.BigDecimal", 1.001);  # workaround

   As mentioned before, method and constructor parameters are converted
automatically between Octave and Java types, if appropriate.  For
functions this is also true with return values, whereas for constructors
this is not.

   It is also possible to access public fields of Java objects from
within Octave using Java syntax, with the limitation of static fields:

     java.math.BigDecimal.ONE;                  # does not work
     java_get ("java.math.BigDecimal", "ONE");  # workaround

   Accordingly, with *note java_set: XREFjava_set. the value of a field
can be set.  Note that only public Java fields are accessible from
within Octave.

   The following example indicates that in Octave empty brackets ‘[]’
represent Java’s ‘null’ value and how Java exceptions are represented.

     javaObject ("java.math.BigDecimal", []);
     ⇒ error: [java] java.lang.NullPointerException

   It is not recommended to represent Java’s ‘null’ value by empty
brackets ‘[]’, because ‘null’ has no type whereas ‘[]’ has type
‘double’.

   In Octave it is possible to provide limited Java reflection by
listing the public fields and methods of a Java object, both static or
not.

     fieldnames (<Java object>)
     methods (<Java object>)

   Finally, an examples is shown how to access the stack trace from
within Octave, where the function *note debug_java: XREFdebug_java. is
used to set and to get the current debug state.  In debug mode, the Java
error and the stack trace are displayed.

     debug_java (true)  # use "false" to omit display of stack trace
     debug_java ()
     ⇒ ans = 1
     javaObject ("java.math.BigDecimal", "1") ...
       .divide (javaObject ("java.math.BigDecimal", "0"))


File: octave.info,  Node: Set up the JVM,  Next: Java Interface Functions,  Prev: How to use Java from within Octave,  Up: Java Interface

A.4.3 Set up the JVM
--------------------

In order to execute Java code Octave creates a Java Virtual Machine
(JVM). By default the version of the JVM is used that was detected
during configuration on Unix-like systems or that is pointed to from the
registry keys at ‘HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\JRE’ or
‘HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\Java Runtime Environment’ on
Windows.  The default path to the JVM can be overridden by setting the
environment variable ‘JAVA_HOME’ to the path where the JVM is installed.
On Windows that might be, for example, ‘C:\Program
Files\Java\jre-10.0.2’.  Make sure that you select a directory that
contains the JVM with a bit-ness that matches Octave’s.

   The JVM is only loaded once per Octave session.  Thus, to change the
used version of the JVM, you might have to re-start Octave.  To check
which version of the JVM is currently being used, run ‘version -java’.

   The JVM allocates a fixed amount of initial memory and may expand
this pool up to a fixed maximum memory limit.  The default values depend
on the Java version (*note javamem: XREFjavamem.).  The memory pool is
shared by all Java objects running in the JVM.  This strict memory limit
is intended mainly to avoid runaway applications inside web browsers or
in enterprise servers which can consume all memory and crash the system.
When the maximum memory limit is hit, Java code will throw exceptions so
that applications will fail or behave unexpectedly.

   You can specify options for the creation of the JVM inside a file
named ‘java.opts’.  This is a text file where enter you enter lines
containing ‘-X’ and ‘-D’ options that are then passed to the JVM during
initialization.

   The directory where the Java options file is located is specified by
the environment variable ‘OCTAVE_JAVA_DIR’.  If unset the directory
where ‘javaclasspath.m’ resides is used instead (typically
‘OCTAVE_HOME/share/octave/OCTAVE_VERSION/m/java/’).  You can find this
directory by executing

     which javaclasspath

   The ‘-X’ options allow you to increase the maximum amount of memory
available to the JVM.  The following example allows up to 256 Megabytes
to be used by adding the following line to the ‘java.opts’ file:

     -Xmx256m

   The maximum possible amount of memory depends on your system.  On a
Windows system with 2 Gigabytes main memory you should be able to set
this maximum to about 1 Gigabyte.

   If your application requires a large amount of memory from the
beginning, you can also specify the initial amount of memory allocated
to the JVM.  Adding the following line to the ‘java.opts’ file starts
the JVM with 64 Megabytes of initial memory:

     -Xms64m

   For more details on the available ‘-X’ options of your Java Virtual
Machine issue the command ‘java -X’ at the operating system command
prompt and consult the Java documentation.

   The ‘-D’ options can be used to define system properties which can
then be used by Java classes inside Octave.  System properties can be
retrieved by using the ‘getProperty()’ methods of the ‘java.lang.System’
class.  The following example line defines the property MYPROPERTY and
assigns it the string ‘12.34’.

     -DMyProperty=12.34

   The value of this property can then be retrieved as a string by a
Java object or in Octave:

     octave> javaMethod ("getProperty", "java.lang.System", "MyProperty");
     ans = 12.34

See also: javamem.


File: octave.info,  Node: Java Interface Functions,  Prev: Set up the JVM,  Up: Java Interface

A.4.4 Java Interface Functions
------------------------------

The following functions are the core of the Java Interface.  They
provide a way to create a Java object, get and set its data fields, and
call Java methods which return results to Octave.

 -- : JOBJ = javaObject (CLASSNAME)
 -- : JOBJ = javaObject (CLASSNAME, ARG1, ...)
     Create a Java object of class CLASSSNAME, by calling the class
     constructor with the arguments ARG1, ...

     The first example below creates an uninitialized object, while the
     second example supplies an initial argument to the constructor.

          x = javaObject ("java.lang.StringBuffer")
          x = javaObject ("java.lang.StringBuffer", "Initial string")

     See also: *note javaMethod: XREFjavaMethod, *note javaArray:
     XREFjavaArray.

 -- : JARY = javaArray (CLASSNAME, SZ)
 -- : JARY = javaArray (CLASSNAME, M, N, ...)

     Create a Java array of size SZ with elements of class CLASSNAME.

     CLASSNAME may be a Java object representing a class or a string
     containing the fully qualified class name.  The size of the object
     may also be specified with individual integer arguments M, N, etc.

     The generated array is uninitialized.  All elements are set to null
     if CLASSNAME is a reference type, or to a default value (usually 0)
     if CLASSNAME is a primitive type.

     Sample code:

          jary = javaArray ("java.lang.String", 2, 2);
          jary(1,1) = "Hello";

     See also: *note javaObject: XREFjavaObject.

   There are many different variable types in Octave, but only ones
created through ‘javaObject’ can use Java functions.  Before using Java
with an unknown object the type can be checked with ‘isjava’.

 -- : isjava (X)
     Return true if X is a Java object.

     See also: *note class: XREFclass, *note typeinfo: XREFtypeinfo,
     *note isa: XREFisa, *note javaObject: XREFjavaObject.

   Once an object has been created it is natural to find out what fields
the object has, and to read (get) and write (set) them.

   In Octave the ‘fieldnames’ function for structures has been
overloaded to return the fields of a Java object.  For example:

     dobj = javaObject ("java.lang.Double", pi);
     fieldnames (dobj)
     ⇒
     {
       [1,1] = public static final double java.lang.Double.POSITIVE_INFINITY
       [1,2] = public static final double java.lang.Double.NEGATIVE_INFINITY
       [1,3] = public static final double java.lang.Double.NaN
       [1,4] = public static final double java.lang.Double.MAX_VALUE
       [1,5] = public static final double java.lang.Double.MIN_NORMAL
       [1,6] = public static final double java.lang.Double.MIN_VALUE
       [1,7] = public static final int java.lang.Double.MAX_EXPONENT
       [1,8] = public static final int java.lang.Double.MIN_EXPONENT
       [1,9] = public static final int java.lang.Double.SIZE
       [1,10] = public static final java.lang.Class java.lang.Double.TYPE
     }

   The analogy of objects with structures is carried over into reading
and writing object fields.  To read a field the object is indexed with
the ‘.’ operator from structures.  This is the preferred method for
reading fields, but Octave also provides a function interface to read
fields with ‘java_get’.  An example of both styles is shown below.

     dobj = javaObject ("java.lang.Double", pi);
     dobj.MAX_VALUE
     ⇒  1.7977e+308
     java_get ("java.lang.Float", "MAX_VALUE")
     ⇒  3.4028e+38

 -- : VAL = java_get (OBJ, NAME)
     Get the value of the field NAME of the Java object OBJ.

     For static fields, OBJ can be a string representing the fully
     qualified name of the corresponding class.

     When OBJ is a regular Java object, structure-like indexing can be
     used as a shortcut syntax.  For instance, the following two
     statements are equivalent

            java_get (x, "field1")
            x.field1

     See also: *note java_set: XREFjava_set, *note javaMethod:
     XREFjavaMethod, *note javaObject: XREFjavaObject.

 -- : OBJ = java_set (OBJ, NAME, VAL)
     Set the value of the field NAME of the Java object OBJ to VAL.

     For static fields, OBJ can be a string representing the fully
     qualified named of the corresponding Java class.

     When OBJ is a regular Java object, structure-like indexing can be
     used as a shortcut syntax.  For instance, the following two
     statements are equivalent

            java_set (x, "field1", val)
            x.field1 = val

     See also: *note java_get: XREFjava_get, *note javaMethod:
     XREFjavaMethod, *note javaObject: XREFjavaObject.

   To see what functions can be called with an object use ‘methods’.
For example, using the previously created DOBJ:

     methods (dobj)
     ⇒
     Methods for class java.lang.Double:
     boolean equals(java.lang.Object)
     java.lang.String toString(double)
     java.lang.String toString()
     ...

   To call a method of an object the same structure indexing operator
‘.’ is used.  Octave also provides a functional interface to calling the
methods of an object through ‘javaMethod’.  An example showing both
styles is shown below.

     dobj = javaObject ("java.lang.Double", pi);
     dobj.equals (3)
     ⇒  0
     javaMethod ("equals", dobj, pi)
     ⇒  1

 -- : RET = javaMethod (METHODNAME, OBJ)
 -- : RET = javaMethod (METHODNAME, OBJ, ARG1, ...)
     Invoke the method METHODNAME on the Java object OBJ with the
     arguments ARG1, ....

     For static methods, OBJ can be a string representing the fully
     qualified name of the corresponding class.

     When OBJ is a regular Java object, structure-like indexing can be
     used as a shortcut syntax.  For instance, the two following
     statements are equivalent

            ret = javaMethod ("method1", x, 1.0, "a string")
            ret = x.method1 (1.0, "a string")

     ‘javaMethod’ returns the result of the method invocation.

     See also: *note methods: XREFmethods, *note javaObject:
     XREFjavaObject.

   The following three functions are used to display and modify the
class path used by the Java Virtual Machine.  This is entirely separate
from Octave’s ‘PATH’ variable and is used by the JVM to find the correct
code to execute.

 -- : javaclasspath ()
 -- : DPATH = javaclasspath ()
 -- : [DPATH, SPATH] = javaclasspath ()
 -- : CLSPATH = javaclasspath (WHAT)
     Return the class path of the Java virtual machine in the form of a
     cell array of strings.

     If called with no inputs:

        • If no output is requested, the dynamic and static classpaths
          are printed to the standard output.

        • If one output value DPATH is requested, the result is the
          dynamic classpath.

        • If two output valuesDPATH and SPATH are requested, the first
          variable will contain the dynamic classpath and the second
          will contain the static classpath.

     If called with a single input parameter WHAT:

     "-dynamic"
          Return the dynamic classpath.

     "-static"
          Return the static classpath.

     "-all"
          Return both the static and dynamic classpath in a single
          cellstr.

     See also: *note javaaddpath: XREFjavaaddpath, *note javarmpath:
     XREFjavarmpath.

 -- : javaaddpath (CLSPATH)
 -- : javaaddpath (CLSPATH1, ...)
     Add CLSPATH to the dynamic class path of the Java virtual machine.

     CLSPATH may either be a directory where ‘.class’ files are found,
     or a ‘.jar’ file containing Java classes.  Multiple paths may be
     added at once by specifying additional arguments.

     See also: *note javarmpath: XREFjavarmpath, *note javaclasspath:
     XREFjavaclasspath.

 -- : javarmpath (CLSPATH)
 -- : javarmpath (CLSPATH1, ...)
     Remove CLSPATH from the dynamic class path of the Java virtual
     machine.

     CLSPATH may either be a directory where ‘.class’ files are found,
     or a ‘.jar’ file containing Java classes.  Multiple paths may be
     removed at once by specifying additional arguments.

     See also: *note javaaddpath: XREFjavaaddpath, *note javaclasspath:
     XREFjavaclasspath.

   The following functions provide information and control over the
interface between Octave and the Java Virtual Machine.

 -- : javachk (FEATURE)
 -- : javachk (FEATURE, CALLER)
 -- : MSG = javachk (...)
     Check for the presence of the Java FEATURE in the current session.
     Return an error structure if FEATURE is not available, not enabled,
     or not recognized.

     Possible recognized features are:

     "awt"
          Abstract Window Toolkit for GUIs.

     "desktop"
          Interactive desktop is running.

     "jvm"
          Java Virtual Machine.

     "swing"
          Swing components for lightweight GUIs.

     If FEATURE is not supported, a scalar struct with field "message"
     and "identifier" is returned.  The field "message" contains an
     error message mentioning FEATURE as well as the optional
     user-specified CALLER.  This structure is suitable for passing in
     to the ‘error’ function.

     If FEATURE is supported and available, an empty struct array is
     returned with fields "message" and "identifier".

     ‘javachk’ determines if specific Java features are available in an
     Octave session.  This function is provided for scripts which may
     alter their behavior based on the availability of Java or specific
     Java runtime features.

     Compatibility Note: The feature "desktop" is never available since
     Octave has no Java-based desktop.

     See also: *note usejava: XREFusejava, *note error: XREFerror.

 -- : usejava (FEATURE)
     Return true if the Java element FEATURE is available.

     Possible features are:

     "awt"
          Abstract Window Toolkit for GUIs.

     "desktop"
          Interactive desktop is running.

     "jvm"
          Java Virtual Machine.

     "swing"
          Swing components for lightweight GUIs.

     ‘usejava’ determines if specific Java features are available in an
     Octave session.  This function is provided for scripts which may
     alter their behavior based on the availability of Java.  The
     feature "desktop" always returns ‘false’ as Octave has no
     Java-based desktop.  Other features may be available if Octave was
     compiled with the Java Interface and Java is installed.

     See also: *note javachk: XREFjavachk.

 -- : javamem ()
 -- : JMEM = javamem ()
     Show the current memory usage of the Java virtual machine (JVM) and
     run the garbage collector.

     When no return argument is given the info is printed to the screen.
     Otherwise, the output cell array JMEM contains Maximum, Total, and
     Free memory (in bytes).

     All Java-based routines are run in the JVM’s shared memory pool, a
     dedicated and separate part of memory claimed by the JVM from your
     computer’s total memory (which comprises physical RAM and virtual
     memory / swap space on hard disk).

     The maximum allowable memory usage can be configured using the file
     ‘java.opts’.  The directory where this file resides is determined
     by the environment variable ‘OCTAVE_JAVA_DIR’.  If unset, the
     directory where ‘javaaddpath.m’ resides is used instead (typically
     ‘OCTAVE_HOME/share/octave/OCTAVE_VERSION/m/java/’).

     ‘java.opts’ is a plain text file with one option per line.  The
     default initial memory size and default maximum memory size (which
     are both system dependent) can be overridden like so:

     -Xms64m

     -Xmx512m

     (in megabytes in this example).  You can adapt these values to your
     own requirements if your system has limited available physical
     memory or if you get Java memory errors.

     "Total memory" is what the operating system has currently assigned
     to the JVM and depends on actual and active memory usage.  "Free
     memory" is self-explanatory.  During operation of Java-based Octave
     functions the amount of Total and Free memory will vary, due to
     Java’s own cleaning up and your operating system’s memory
     management.

 -- : VAL = java_matrix_autoconversion ()
 -- : OLD_VAL = java_matrix_autoconversion (NEW_VAL)
 -- : java_matrix_autoconversion (NEW_VAL, "local")
     Query or set the internal variable that controls whether Java
     arrays are automatically converted to Octave matrices.

     The default value is false.

     When called from inside a function with the "local" option, the
     variable is changed locally for the function and any subroutines it
     calls.  The original variable value is restored when exiting the
     function.

     See also: *note java_unsigned_autoconversion:
     XREFjava_unsigned_autoconversion, *note debug_java: XREFdebug_java.

 -- : VAL = java_unsigned_autoconversion ()
 -- : OLD_VAL = java_unsigned_autoconversion (NEW_VAL)
 -- : java_unsigned_autoconversion (NEW_VAL, "local")
     Query or set the internal variable that controls how integer
     classes are converted when ‘java_matrix_autoconversion’ is enabled.

     When enabled, Java arrays of class Byte or Integer are converted to
     matrices of class uint8 or uint32 respectively.  The default value
     is true.

     When called from inside a function with the "local" option, the
     variable is changed locally for the function and any subroutines it
     calls.  The original variable value is restored when exiting the
     function.

     See also: *note java_matrix_autoconversion:
     XREFjava_matrix_autoconversion, *note debug_java: XREFdebug_java.

 -- : VAL = debug_java ()
 -- : OLD_VAL = debug_java (NEW_VAL)
 -- : debug_java (NEW_VAL, "local")
     Query or set the internal variable that determines whether extra
     debugging information regarding the initialization of the JVM and
     any Java exceptions is printed.

     When called from inside a function with the "local" option, the
     variable is changed locally for the function and any subroutines it
     calls.  The original variable value is restored when exiting the
     function.

     See also: *note java_matrix_autoconversion:
     XREFjava_matrix_autoconversion, *note java_unsigned_autoconversion:
     XREFjava_unsigned_autoconversion.


File: octave.info,  Node: Test and Demo Functions,  Next: Obsolete Functions,  Prev: External Code Interface,  Up: Top

Appendix B Test and Demo Functions
**********************************

Octave includes a number of functions to allow the integration of
testing and demonstration code in the source code of the functions
themselves.

* Menu:

* Test Functions::
* Demonstration Functions::


File: octave.info,  Node: Test Functions,  Next: Demonstration Functions,  Up: Test and Demo Functions

B.1 Test Functions
==================

 -- : test NAME
 -- : test NAME quiet|normal|verbose
 -- : test ("NAME", "quiet|normal|verbose", FID)
 -- : test ("NAME", "quiet|normal|verbose", FNAME)
 -- : SUCCESS = test (...)
 -- : [N, NMAX, NXFAIL, NBUG, NSKIP, NRTSKIP, NREGRESSION] = test (...)
 -- : [CODE, IDX] = test ("NAME", "grabdemo")
 -- : test ([], "explain", FID)
 -- : test ([], "explain", FNAME)

     Perform built-in self-tests from the first file in the loadpath
     matching NAME.

     ‘test’ can be called in either command or functional form.  The
     exact operation of test is determined by a combination of mode
     (interactive or batch), reporting level ("quiet", "normal",
     "verbose"), and whether a logfile or summary output variable is
     used.

     The default mode when ‘test’ is called from the command line is
     interactive.  In this mode, tests will be run until the first error
     is encountered, or all tests complete successfully.  In batch mode,
     all tests are run regardless of any failures, and the results are
     collected for reporting.  Tests which require user interaction,
     i.e., demo blocks, are never run in batch mode.

     Batch mode is enabled by either 1) specifying a logfile using the
     third argument FNAME or FID, or 2) requesting an output argument
     such as SUCCESS, N, etc.

     The optional second argument determines the amount of output to
     generate and which types of tests to run.  The default value is
     "normal".  Requesting an output argument will suppress printing the
     final summary message and any intermediate warnings, unless verbose
     reporting is enabled.

     "quiet"
          Print a summary message when all tests pass, or print an error
          with the results of the first bad test when a failure occurs.
          Don’t run tests which require user interaction.

     "normal"
          Display warning messages about skipped tests or failing xtests
          during test execution.  Print a summary message when all tests
          pass, or print an error with the results of the first bad test
          when a failure occurs.  Don’t run tests which require user
          interaction.

     "verbose"
          Display tests before execution.  Print all warning messages.
          In interactive mode, run all tests including those which
          require user interaction.

     The optional third input argument specifies a logfile where results
     of the tests should be written.  The logfile may be a character
     string (FNAME) or an open file descriptor ID (FID).  To enable
     batch processing, but still print the results to the screen, use
     ‘stdout’ for FID.

     When called with just a single output argument SUCCESS, ‘test’
     returns true if all of the tests were successful.  If called with
     more than one output argument then the number of successful tests
     (N), the total number of tests in the file (NMAX), the number of
     xtest failures (NXFAIL), the number of tests failed due known bugs
     (NBUG), the number of tests skipped due to missing features
     (NSKIP), the number of tests skipped due to run-time conditions
     (NRTSKIP), and the number of regressions (NREGRESSION) are
     returned.

     Example

          test sind
          ⇒
          PASSES 5 out of 5 tests

          [n, nmax] = test ("sind")
          ⇒
          n =  5
          nmax =  5

     Additional Calling Syntaxes

     If the second argument is the string "grabdemo", the contents of
     any built-in demo blocks are extracted but not executed.  The text
     for all code blocks is concatenated and returned as CODE with IDX
     being a vector of positions of the ends of each demo block.  For an
     easier way to extract demo blocks from files, *Note example:
     XREFexample.

     If the second argument is "explain" then NAME is ignored and an
     explanation of the line markers used in ‘test’ output reports is
     written to the file specified by FNAME or FID.

     See also: *note assert: XREFassert, *note fail: XREFfail, *note
     demo: XREFdemo, *note example: XREFexample, *note error: XREFerror.

   ‘test’ scans the named script file looking for lines which start with
the identifier ‘%!’.  The prefix is stripped off and the rest of the
line is processed through the Octave interpreter.  If the code generates
an error, then the test is said to fail.

   Since ‘eval()’ will stop at the first error it encounters, you must
divide your tests up into blocks, with anything in a separate block
evaluated separately.  Blocks are introduced by valid keywords like
‘test’, ‘function’, or ‘assert’ immediately following ‘%!’.  A block is
defined by indentation as in Python.  Lines beginning with
‘%!<whitespace>’ are part of the preceeding block.

   For example:

     %!test error ("this test fails!")
     %!test "test doesn't fail.  it doesn't generate an error"

   When a test fails, you will see something like:

       ***** test error ("this test fails!")
     !!!!! test failed
     this test fails!

   Generally, to test if something works, you want to assert that it
produces a correct value.  A real test might look something like

     %!test
     %! A = [1, 2, 3; 4, 5, 6]; B = [1; 2];
     %! expect = [ A ; 2*A ];
     %! get = kron (B, A);
     %! if (any (size (expect) != size (get)))
     %!   error ("wrong size: expected %d,%d but got %d,%d",
     %!          size (expect), size (get));
     %! elseif (any (any (expect != get)))
     %!   error ("didn't get what was expected.");
     %! endif

   To make the process easier, use the ‘assert’ function.  For example,
with ‘assert’ the previous test is reduced to:

     %!test
     %! A = [1, 2, 3; 4, 5, 6]; B = [1; 2];
     %! assert (kron (B, A), [ A; 2*A ]);

   ‘assert’ can accept a tolerance so that you can compare results
absolutely or relatively.  For example, the following all succeed:

     %!test assert (1+eps, 1, 2*eps)           # absolute error
     %!test assert (100+100*eps, 100, -2*eps)  # relative error

   You can also do the comparison yourself, but still have assert
generate the error:

     %!test assert (isempty ([]))
     %!test assert ([1, 2; 3, 4] > 0)

   Because ‘assert’ is so frequently used alone in a test block, there
is a shorthand form:

     %!assert (...)

which is equivalent to:

     %!test assert (...)

   Occasionally a block of tests will depend on having optional
functionality in Octave.  Before testing such blocks the availability of
the required functionality must be checked.  A ‘%!testif HAVE_XXX’ block
will only be run if Octave was compiled with functionality ‘HAVE_XXX’.
For example, the sparse single value decomposition, ‘svds()’, depends on
having the ARPACK library.  All of the tests for ‘svds’ begin with

     %!testif HAVE_ARPACK

Review ‘config.h’ or ‘__octave_config_info__ ("build_features")’ to see
some of the possible values to check.

   Sometimes during development there is a test that should work but is
known to fail.  You still want to leave the test in because when the
final code is ready the test should pass, but you may not be able to fix
it immediately.  To avoid unnecessary bug reports for these known
failures, mark the block with ‘xtest’ rather than ‘test’:

     %!xtest assert (1==0)
     %!xtest fail ("success=1", "error")

In this case, the test will run and any failure will be reported.
However, testing is not aborted and subsequent test blocks will be
processed normally.  Another use of ‘xtest’ is for statistical tests
which should pass most of the time but are known to fail occasionally.

   Each block is evaluated in its own function environment, which means
that variables defined in one block are not automatically shared with
other blocks.  If you do want to share variables, then you must declare
them as ‘shared’ before you use them.  For example, the following
declares the variable A, gives it an initial value (default is empty),
and then uses it in several subsequent tests.

     %!shared A
     %! A = [1, 2, 3; 4, 5, 6];
     %!assert (kron ([1; 2], A), [ A; 2*A ])
     %!assert (kron ([1, 2], A), [ A, 2*A ])
     %!assert (kron ([1,2; 3,4], A), [ A,2*A; 3*A,4*A ])

   You can share several variables at the same time:

     %!shared A, B

   You can also share test functions:

     %!function A = fn (B)
     %!  A = 2*B;
     %!endfunction
     %!assert (fn(2), 4)

   Note that all previous variables and values are lost when a new
shared block is declared.

   Remember that ‘%!function’ begins a new block and that
‘%!endfunction’ ends this block.  Be aware that until a new block is
started, lines starting with ‘%!<space>’ will be discarded as comments.
The following is nearly identical to the example above, but does
nothing.

     %!function A = fn (B)
     %!  A = 2*B;
     %!endfunction
     %! assert (fn(2), 4)

Because there is a space after ‘%!’ the ‘assert’ statement does not
begin a new block and this line is treated as a comment.

   Error and warning blocks are like test blocks, but they only succeed
if the code generates an error.  You can check the text of the error is
correct using an optional regular expression ‘<pattern>’.  For example:

     %!error <passes!> error ("this test passes!")

   If the code doesn’t generate an error, the test fails.  For example:

     %!error "this is an error because it succeeds."

produces

       ***** error "this is an error because it succeeds."
     !!!!! test failed: no error

   It is important to automate the tests as much as possible, however
some tests require user interaction.  These can be isolated into demo
blocks, which if you are in batch mode, are only run when called with
‘demo’ or the ‘verbose’ option to ‘test’.  The code is displayed before
it is executed.  For example,

     %!demo
     %! T = [0:0.01:2*pi]; X = sin (T);
     %! plot (T, X);
     %! # you should now see a sine wave in your figure window

produces

     funcname example 1:
      T = [0:0.01:2*pi]; X = sin (T);
      plot (T, X);
      # you should now see a sine wave in your figure window

     Press <enter> to continue:

   Note that demo blocks cannot use any shared variables.  This is so
that they can be executed by themselves, ignoring all other tests.

   If you want to temporarily disable a test block, put ‘#’ in place of
the block type.  This creates a comment block which is echoed in the log
file but not executed.  For example:

     %!#demo
     %! T = [0:0.01:2*pi]; X = sin (T);
     %! plot (T, X);
     %! # you should now see a sine wave in your figure window

The following trivial code snippet provides examples for the use of
fail, assert, error, and xtest:

     function OUTPUT = must_be_zero (INPUT)
       if (INPUT != 0)
         error ("Nonzero input!")
       endif
       OUTPUT = INPUT;
     endfunction

     %!fail ("must_be_zero (1)")
     %!assert (must_be_zero (0), 0)
     %!error <Nonzero> must_be_zero (1)
     %!xtest error ("This code generates an error")

When putting this in a file ‘must_be_zero.m’, and running the test, we
see

     test must_be_zero verbose

     ⇒
     >>>>> /path/to/must_be_zero.m
     ***** fail ("must_be_zero (1)")
     ***** assert (must_be_zero (0), 0)
     ***** error <Nonzero> must_be_zero (1)
     ***** xtest error ("This code generates an error")
     !!!!! known failure
     This code generates an error
     PASSES 3 out of 4 tests (1 expected failure)

Block type summary:
...................

‘%!test’
‘%!test <MESSAGE>’
     Check that entire block is correct.  If ‘<MESSAGE>’ is present, the
     test block is interpreted as for ‘xtest’.

‘%!testif HAVE_XXX’
‘%!testif HAVE_XXX, HAVE_YYY, ...’
‘%!testif HAVE_XXX, HAVE_YYY ...; RUNTIME_COND’
‘%!testif ... <MESSAGE>’
     Check block only if Octave was compiled with feature ‘HAVE_XXX’.
     ‘RUNTIME_COND’ is an optional expression to evaluate to check
     whether some condition is met when the test is executed.  If
     ‘RUNTIME_COND’ is false, the test is skipped.  If ‘<MESSAGE>’ is
     present, the test block is interpreted as for ‘xtest’.

‘%!xtest’
‘%!xtest <MESSAGE>’
     Check block, report a test failure but do not abort testing.  If
     ‘<MESSAGE>’ is present, then the text of the message is displayed
     if the test fails, like this:

          !!!!! Known bug:  MESSAGE

     If the message is an integer, it is interpreted as a bug ID for the
     Octave bug tracker and reported as

          !!!!! Known bug: https://octave.org/testfailure/?BUG-ID

     in which BUG-ID is the integer bug number.  The intent is to allow
     clearer documentation of known problems.

‘%!error’
‘%!error <MESSAGE>’
‘%!warning’
‘%!warning <MESSAGE>’
     Check for correct error or warning message.  If ‘<MESSAGE>’ is
     supplied it is interpreted as a regular expression pattern that is
     expected to match the error or warning message.

‘%!demo’
     Demo only executes in interactive mode.

‘%!#’
     Comment.  Ignore everything within the block

‘%!shared x,y,z’
     Declare variables for use in multiple tests.

‘%!function’
     Define a function for use in multiple tests.

‘%!endfunction’
     Close a function definition.

‘%!assert (x, y, tol)’

‘%!assert <MESSAGE> (x, y, tol)’

‘%!fail (CODE, PATTERN)’

‘%!fail <MESSAGE> (CODE, PATTERN)’
     Shorthand for ‘%!test assert (x, y, tol)’ or ‘%!test fail (CODE,
     PATTERN)’.  If ‘<MESSAGE>’ is present, the test block is
     interpreted as for ‘xtest’.

   When coding tests the Octave convention is that lines that begin with
a block type do not have a semicolon at the end.  Any code that is
within a block, however, is normal Octave code and usually will have a
trailing semicolon.  For example,

     ## bare block instantiation
     %!assert (sin (0), 0)

but

     ## test block with normal Octave code
     %!test
     %! assert (sin (0), 0);

   You can also create test scripts for built-in functions and your own
C++ functions.  To do so, put a file with the bare function name (no .m
extension) in a directory in the load path and it will be discovered by
the ‘test’ function.  Alternatively, you can embed tests directly in
your C++ code:

     /*
     %!test disp ("this is a test")
     */

or

     #if 0
     %!test disp ("this is a test")
     #endif

However, in this case the raw source code will need to be on the load
path and the user will have to remember to type ‘test ("funcname.cc")’.

 -- : assert (COND)
 -- : assert (COND, ERRMSG)
 -- : assert (COND, ERRMSG, ...)
 -- : assert (COND, MSG_ID, ERRMSG, ...)
 -- : assert (OBSERVED, EXPECTED)
 -- : assert (OBSERVED, EXPECTED, TOL)

     Produce an error if the specified condition is not met.

     ‘assert’ can be called in three different ways.

     ‘assert (COND)’
     ‘assert (COND, ERRMSG)’
     ‘assert (COND, ERRMSG, ...)’
     ‘assert (COND, MSG_ID, ERRMSG, ...)’
          Called with a single argument COND, ‘assert’ produces an error
          if COND is false (numeric zero).

          Any additional arguments are passed to the ‘error’ function
          for processing.

     ‘assert (OBSERVED, EXPECTED)’
          Produce an error if observed is not the same as expected.

          Note that OBSERVED and EXPECTED can be scalars, vectors,
          matrices, strings, cell arrays, or structures.

     ‘assert (OBSERVED, EXPECTED, TOL)’
          Produce an error if observed is not the same as expected but
          equality comparison for numeric data uses a tolerance TOL.

          If TOL is positive then it is an absolute tolerance which will
          produce an error if ‘abs (OBSERVED - EXPECTED) > abs (TOL)’.

          If TOL is negative then it is a relative tolerance which will
          produce an error if ‘abs (OBSERVED - EXPECTED) > abs (TOL *
          EXPECTED)’.

          If EXPECTED is zero TOL will always be interpreted as an
          absolute tolerance.

          If TOL is not scalar its dimensions must agree with those of
          OBSERVED and EXPECTED and tests are performed on an
          element-by-element basis.

     See also: *note fail: XREFfail, *note test: XREFtest, *note error:
     XREFerror, *note isequal: XREFisequal.

 -- : fail (CODE)
 -- : fail (CODE, PATTERN)
 -- : fail (CODE, "warning")
 -- : fail (CODE, "warning", PATTERN)

     Return true if CODE fails with an error message matching PATTERN,
     otherwise produce an error.

     CODE must be in the form of a string that is passed to the Octave
     interpreter via the ‘evalin’ function, i.e., a (quoted) string
     constant or a string variable.

     Note that if CODE runs successfully, rather than failing, the error
     printed is:

                    expected error <.> but got none

     If called with two arguments, the return value will be true only if
     CODE fails with an error message containing PATTERN (case
     sensitive).  If the code fails with a different error than the one
     specified in PATTERN then the message produced is:

                    expected <PATTERN>
                    but got <text of actual error>

     The angle brackets are not part of the output.

     When called with the "warning" option ‘fail’ will produce an error
     if executing the code produces no warning.

     See also: *note assert: XREFassert, *note error: XREFerror.


File: octave.info,  Node: Demonstration Functions,  Prev: Test Functions,  Up: Test and Demo Functions

B.2 Demonstration Functions
===========================

 -- : demo NAME
 -- : demo NAME N
 -- : demo ("NAME")
 -- : demo ("NAME", N)

     Run example code block N associated with the function NAME.

     If N is not specified, all examples are run.

     The preferred location for example code blocks is embedded within
     the script m-file immediately following the code that it exercises.
     Alternatively, the examples may be stored in a file with the same
     name but no extension located on Octave’s load path.  To separate
     examples from regular script code all lines are prefixed by ‘%!’.
     Each example must also be introduced by the keyword "demo" flush
     left to the prefix with no intervening spaces.  The remainder of
     the example can contain arbitrary Octave code.  For example:

          %!demo
          %! t = 0:0.01:2*pi;
          %! x = sin (t);
          %! plot (t, x);
          %! title ("one cycle of a sine wave");
          %! #-------------------------------------------------
          %! # the figure window shows one cycle of a sine wave

     Note that the code is displayed before it is executed so that a
     simple comment at the end suffices for labeling what is being
     shown.  For plots, labeling can also be done with ‘title’ or
     ‘text’.  It is generally *not* necessary to use ‘disp’ or ‘printf’
     within the demo.

     Demos are run in a stand-alone function environment with no access
     to external variables.  This means that every demo must have
     separate initialization code.  Alternatively, all demos can be
     combined into a single large demo with the code

          %! input ("Press <enter> to continue: ", "s");

     between the sections, but this usage is discouraged.  Other
     techniques to avoid multiple initialization blocks include using
     multiple plots with a new ‘figure’ command between each plot, or
     using ‘subplot’ to put multiple plots in the same window.

     Finally, because ‘demo’ evaluates within a function context it is
     not possible to define new functions within the code.  Anonymous
     functions make a good substitute in most instances.  If function
     blocks *must* be used then the code ‘eval (example ("function",
     n))’ will allow Octave to see them.  This has its own problems,
     however, as ‘eval’ only evaluates one line or statement at a time.
     In this case the function declaration must be wrapped with "if 1
     <demo stuff> endif" where "if" is on the same line as "demo".  For
     example:

          %!demo if 1
          %!  function y = f(x)
          %!    y = x;
          %!  endfunction
          %!  f(3)
          %! endif

     See also: *note rundemos: XREFrundemos, *note example: XREFexample,
     *note test: XREFtest.

 -- : example NAME
 -- : example NAME N
 -- : example ("NAME")
 -- : example ("NAME", N)
 -- : [S, IDX] = example (...)

     Display the code for example N associated with the function NAME,
     but do not run it.

     If N is not specified, all examples are displayed.

     When called with output arguments, the examples are returned in the
     form of a string S, with IDX indicating the ending position of the
     various examples.

     See ‘demo’ for a complete explanation.

     See also: *note demo: XREFdemo, *note test: XREFtest.

 -- : rundemos ()
 -- : rundemos (DIRECTORY)
     Execute built-in demos for all m-files in the specified DIRECTORY.

     Demo blocks in any C++ source files (‘*.cc’) will also be executed
     for use with dynamically linked oct-file functions.

     If no directory is specified, operate on all directories in
     Octave’s search path for functions.

     See also: *note demo: XREFdemo, *note runtests: XREFruntests, *note
     path: XREFpath.

 -- : runtests ()
 -- : runtests (DIRECTORY)
     Execute built-in tests for all m-files in the specified DIRECTORY.

     Test blocks in any C++ source files (‘*.cc’) will also be executed
     for use with dynamically linked oct-file functions.

     If no directory is specified, operate on all directories in
     Octave’s search path for functions.

     See also: *note rundemos: XREFrundemos, *note test: XREFtest, *note
     path: XREFpath.

 -- : speed (F, INIT, MAX_N, F2, TOL)
 -- : [ORDER, N, T_F, T_F2] = speed (...)

     Determine the execution time of an expression (F) for various input
     values (N).

     The N are log-spaced from 1 to MAX_N.  For each N, an
     initialization expression (INIT) is computed to create any data
     needed for the test.  If a second expression (F2) is given then the
     execution times of the two expressions are compared.  When called
     without output arguments the results are printed to stdout and
     displayed graphically.

     ‘F’
          The code expression to evaluate.

     ‘MAX_N’
          The maximum test length to run.  The default value is 100.
          Alternatively, use ‘[min_n, max_n]’ or specify the N exactly
          with ‘[n1, n2, ..., nk]’.

     ‘INIT’
          Initialization expression for function argument values.  Use K
          for the test number and N for the size of the test.  This
          should compute values for all variables used by F.  Note that
          INIT will be evaluated first for k = 0, so things which are
          constant throughout the test series can be computed once.  The
          default value is ‘X = randn (N, 1)’.

     ‘F2’
          An alternative expression to evaluate, so that the speed of
          two expressions can be directly compared.  The default is
          ‘[]’.

     ‘TOL’
          Tolerance used to compare the results of expression F and
          expression F2.  If TOL is positive, the tolerance is an
          absolute one.  If TOL is negative, the tolerance is a relative
          one.  The default is ‘eps’.  If TOL is ‘Inf’, then no
          comparison will be made.

     ‘ORDER’
          The time complexity of the expression O(a*n^p).  This is a
          structure with fields ‘a’ and ‘p’.

     ‘N’
          The values N for which the expression was calculated *AND* the
          execution time was greater than zero.

     ‘T_F’
          The nonzero execution times recorded for the expression F in
          seconds.

     ‘T_F2’
          The nonzero execution times recorded for the expression F2 in
          seconds.  If required, the mean time ratio is simply ‘mean
          (T_f ./ T_f2)’.

     The slope of the execution time graph shows the approximate power
     of the asymptotic running time O(n^p).  This power is plotted for
     the region over which it is approximated (the latter half of the
     graph).  The estimated power is not very accurate, but should be
     sufficient to determine the general order of an algorithm.  It
     should indicate if, for example, the implementation is unexpectedly
     O(n^2) rather than O(n) because it extends a vector each time
     through the loop rather than pre-allocating storage.  In the
     current version of Octave, the following is not the expected O(n).

          speed ("for i = 1:n, y{i} = x(i); endfor", "", [1000, 10000])

     But it is if you preallocate the cell array ‘y’:

          speed ("for i = 1:n, y{i} = x(i); endfor", ...
                 "x = rand (n, 1); y = cell (size (x));", [1000, 10000])

     An attempt is made to approximate the cost of individual
     operations, but it is wildly inaccurate.  You can improve the
     stability somewhat by doing more work for each ‘n’.  For example:

          speed ("airy(x)", "x = rand (n, 10)", [10000, 100000])

     When comparing two different expressions (F, F2), the slope of the
     line on the speedup ratio graph should be larger than 1 if the new
     expression is faster.  Better algorithms have a shallow slope.
     Generally, vectorizing an algorithm will not change the slope of
     the execution time graph, but will shift it relative to the
     original.  For example:

          speed ("sum (x)", "", [10000, 100000], ...
                 "v = 0; for i = 1:length (x), v += x(i); endfor")

     The following is a more complex example.  If there was an original
     version of ‘xcorr’ using for loops and a second version using an
     FFT, then one could compare the run speed for various lags as
     follows, or for a fixed lag with varying vector lengths as follows:

          speed ("xcorr (x, n)", "x = rand (128, 1);", 100,
                 "xcorr_orig (x, n)", -100*eps)
          speed ("xcorr (x, 15)", "x = rand (20+n, 1);", 100,
                 "xcorr_orig (x, n)", -100*eps)

     Assuming one of the two versions is in xcorr_orig, this would
     compare their speed and their output values.  Note that the FFT
     version is not exact, so one must specify an acceptable tolerance
     on the comparison ‘100*eps’.  In this case, the comparison should
     be computed relatively, as ‘abs ((X - Y) ./ Y)’ rather than
     absolutely as ‘abs (X - Y)’.

     Type ‘example ("speed")’ to see some real examples or ‘demo
     ("speed")’ to run them.


File: octave.info,  Node: Obsolete Functions,  Next: Trouble,  Prev: Test and Demo Functions,  Up: Top

Appendix C Obsolete Functions
*****************************

After being marked as deprecated for two major releases, the following
functions have been removed from Octave.  The third column of the table
shows the version of Octave in which the function was removed.  Prior to
removal, each function in the list was marked as deprecated for at least
two major releases.  All deprecated functions issue warnings explaining
that they will be removed in a future version of Octave, and which
function should be used instead.

   Replacement functions do not always accept precisely the same
arguments as the obsolete function, but should provide equivalent
functionality.

Obsolete Function      Replacement            Version
----------------------------------------------------------
‘beta_cdf’             ‘betacdf’ in Octave    3.4.0
                       Forge statistics pkg
‘beta_inv’             ‘betainv’ in Octave    3.4.0
                       Forge statistics pkg
‘beta_pdf’             ‘betapdf’ in Octave    3.4.0
                       Forge statistics pkg
‘beta_rnd’             ‘betarnd’ in Octave    3.4.0
                       Forge statistics pkg
‘binomial_cdf’         ‘binocdf’ in Octave    3.4.0
                       Forge statistics pkg
‘binomial_inv’         ‘binoinv’ in Octave    3.4.0
                       Forge statistics pkg
‘binomial_pdf’         ‘binopdf’ in Octave    3.4.0
                       Forge statistics pkg
‘binomial_rnd’         ‘binornd’ in Octave    3.4.0
                       Forge statistics pkg
‘chisquare_cdf’        ‘chi2cdf’ in Octave    3.4.0
                       Forge statistics pkg
‘chisquare_inv’        ‘chi2inv’ in Octave    3.4.0
                       Forge statistics pkg
‘chisquare_pdf’        ‘chi2pdf’ in Octave    3.4.0
                       Forge statistics pkg
‘chisquare_rnd’        ‘chi2rnd’ in Octave    3.4.0
                       Forge statistics pkg
‘clearplot’            ‘clf’                  3.4.0
‘com2str’              ‘num2str’              3.4.0
‘exponential_cdf’      ‘expcdf’ in Octave     3.4.0
                       Forge statistics pkg
‘exponential_inv’      ‘expinv’ in Octave     3.4.0
                       Forge statistics pkg
‘exponential_pdf’      ‘exppdf’ in Octave     3.4.0
                       Forge statistics pkg
‘exponential_rnd’      ‘exprnd’ in Octave     3.4.0
                       Forge statistics pkg
‘f_cdf’                ‘fcdf’ in Octave       3.4.0
                       Forge statistics pkg
‘f_inv’                ‘finv’ in Octave       3.4.0
                       Forge statistics pkg
‘f_pdf’                ‘fpdf’ in Octave       3.4.0
                       Forge statistics pkg
‘f_rnd’                ‘frnd’ in Octave       3.4.0
                       Forge statistics pkg
‘gamma_cdf’            ‘gamcdf’ in Octave     3.4.0
                       Forge statistics pkg
‘gamma_inv’            ‘gaminv’ in Octave     3.4.0
                       Forge statistics pkg
‘gamma_pdf’            ‘gampdf’ in Octave     3.4.0
                       Forge statistics pkg
‘gamma_rnd’            ‘gamrnd’ in Octave     3.4.0
                       Forge statistics pkg
‘geometric_cdf’        ‘geocdf’ in Octave     3.4.0
                       Forge statistics pkg
‘geometric_inv’        ‘geoinv’ in Octave     3.4.0
                       Forge statistics pkg
‘geometric_pdf’        ‘geopdf’ in Octave     3.4.0
                       Forge statistics pkg
‘geometric_rnd’        ‘geornd’ in Octave     3.4.0
                       Forge statistics pkg
‘hypergeometric_cdf’   ‘hygecdf’ in Octave    3.4.0
                       Forge statistics pkg
‘hypergeometric_inv’   ‘hygeinv’ in Octave    3.4.0
                       Forge statistics pkg
‘hypergeometric_pdf’   ‘hygepdf’ in Octave    3.4.0
                       Forge statistics pkg
‘hypergeometric_rnd’   ‘hygernd’ in Octave    3.4.0
                       Forge statistics pkg
‘intersection’         ‘intersect’            3.4.0
‘is_bool’              ‘isbool’               3.4.0
‘is_complex’           ‘iscomplex’            3.4.0
‘is_list’              None                   3.4.0
‘is_matrix’            ‘ismatrix’             3.4.0
‘is_scalar’            ‘isscalar’             3.4.0
‘is_square’            ‘issquare’             3.4.0
‘is_stream’            None                   3.4.0
‘is_struct’            ‘isstruct’             3.4.0
‘is_symmetric’         ‘issymmetric’          3.4.0
‘is_vector’            ‘isvector’             3.4.0
‘lognormal_cdf’        ‘logncdf’ in Octave    3.4.0
                       Forge statistics pkg
‘lognormal_inv’        ‘logninv’ in Octave    3.4.0
                       Forge statistics pkg
‘lognormal_pdf’        ‘lognpdf’ in Octave    3.4.0
                       Forge statistics pkg
‘lognormal_rnd’        ‘lognrnd’ in Octave    3.4.0
                       Forge statistics pkg
‘meshdom’              ‘meshgrid’             3.4.0
‘normal_cdf’           ‘normcdf’ in Octave    3.4.0
                       Forge statistics pkg
‘normal_inv’           ‘norminv’ in Octave    3.4.0
                       Forge statistics pkg
‘normal_pdf’           ‘normpdf’ in Octave    3.4.0
                       Forge statistics pkg
‘normal_rnd’           ‘normrnd’ in Octave    3.4.0
                       Forge statistics pkg
‘pascal_cdf’           ‘nbincdf’ in Octave    3.4.0
                       Forge statistics pkg
‘pascal_inv’           ‘nbininv’ in Octave    3.4.0
                       Forge statistics pkg
‘pascal_pdf’           ‘nbinpdf’ in Octave    3.4.0
                       Forge statistics pkg
‘pascal_rnd’           ‘nbinrnd’ in Octave    3.4.0
                       Forge statistics pkg
‘poisson_cdf’          ‘poisscdf’ in Octave   3.4.0
                       Forge statistics pkg
‘poisson_inv’          ‘poissinv’ in Octave   3.4.0
                       Forge statistics pkg
‘poisson_pdf’          ‘poisspdf’ in Octave   3.4.0
                       Forge statistics pkg
‘poisson_rnd’          ‘poissrnd’ in Octave   3.4.0
                       Forge statistics pkg
‘polyinteg’            ‘polyint’              3.4.0
‘struct_contains’      ‘isfield’              3.4.0
‘struct_elements’      ‘fieldnames’           3.4.0
‘t_cdf’                ‘tcdf’ in Octave       3.4.0
                       Forge statistics pkg
‘t_inv’                ‘tinv’ in Octave       3.4.0
                       Forge statistics pkg
‘t_pdf’                ‘tpdf’ in Octave       3.4.0
                       Forge statistics pkg
‘t_rnd’                ‘trnd’ in Octave       3.4.0
                       Forge statistics pkg
‘uniform_cdf’          ‘unifcdf’ in Octave    3.4.0
                       Forge statistics pkg
‘uniform_inv’          ‘unifinv’ in Octave    3.4.0
                       Forge statistics pkg
‘uniform_pdf’          ‘unifpdf’ in Octave    3.4.0
                       Forge statistics pkg
‘uniform_rnd’          ‘unifrnd’ in Octave    3.4.0
                       Forge statistics pkg
‘weibull_cdf’          ‘wblcdf’ in Octave     3.4.0
                       Forge statistics pkg
‘weibull_inv’          ‘wblinv’ in Octave     3.4.0
                       Forge statistics pkg
‘weibull_pdf’          ‘wblpdf’ in Octave     3.4.0
                       Forge statistics pkg
‘weibull_rnd’          ‘wblrnd’ in Octave     3.4.0
                       Forge statistics pkg
‘wiener_rnd’           ‘wienrnd’ in Octave    3.4.0
                       Forge statistics pkg
‘create_set’           ‘unique’               3.6.0
‘dmult’                ‘diag (A) * B’         3.6.0
‘iscommand’            None                   3.6.0
‘israwcommand’         None                   3.6.0
‘lchol’                ‘chol (...,            3.6.0
                       "lower")’
‘loadimage’            ‘load’ or ‘imread’     3.6.0
‘mark_as_command’      None                   3.6.0
‘mark_as_rawcommand’   None                   3.6.0
‘spatan2’              ‘atan2’                3.6.0
‘spchol’               ‘chol’                 3.6.0
‘spchol2inv’           ‘chol2inv’             3.6.0
‘spcholinv’            ‘cholinv’              3.6.0
‘spcumprod’            ‘cumprod’              3.6.0
‘spcumsum’             ‘cumsum’               3.6.0
‘spdet’                ‘det’                  3.6.0
‘spdiag’               ‘sparse (diag          3.6.0
                       (...))’
‘spfind’               ‘find’                 3.6.0
‘sphcat’               ‘horzcat’              3.6.0
‘spinv’                ‘inv’                  3.6.0
‘spkron’               ‘kron’                 3.6.0
‘splchol’              ‘chol (...,            3.6.0
                       "lower")’
‘split’                ‘char (strsplit (s,    3.6.0
                       t))’
‘splu’                 ‘lu’                   3.6.0
‘spmax’                ‘max’                  3.6.0
‘spmin’                ‘min’                  3.6.0
‘spprod’               ‘prod’                 3.6.0
‘spqr’                 ‘qr’                   3.6.0
‘spsum’                ‘sum’                  3.6.0
‘spsumsq’              ‘sumsq’                3.6.0
‘spvcat’               ‘vertcat’              3.6.0
‘str2mat’              ‘char’                 3.6.0
‘unmark_command’       None                   3.6.0
‘unmark_rawcommand’    None                   3.6.0
‘autocor’              ‘xcorr’ in Octave      3.8.0
                       Forge signal pkg
‘autocov’              ‘xcov’ in Octave       3.8.0
                       Forge signal pkg
‘betai’                ‘betainc’              3.8.0
‘cellidx’              ‘ismember’             3.8.0
‘cquad’                ‘quadcc’               3.8.0
‘dispatch’             None                   3.8.0
‘fstat’                ‘stat’                 3.8.0
‘gammai’               ‘gammainc’             3.8.0
‘glpkmex’              ‘glpk’                 3.8.0
‘is_duplicate_entry’   ‘unique’               3.8.0
‘is_global’            ‘isglobal’             3.8.0
‘krylovb’              ‘[Uret, ~, Ucols] =    3.8.0
                       krylov (...)’
‘perror’               None                   3.8.0
‘replot’               ‘refresh’              3.8.0
‘saveimage’            ‘imwrite’              3.8.0
‘setstr’               ‘char’                 3.8.0
‘strerror’             None                   3.8.0
‘values’               ‘unique’               3.8.0
‘cut’                  ‘histc’                4.0.0
‘cor’                  ‘corr’                 4.0.0
‘corrcoef’             ‘corr’                 4.0.0
‘__error_text__’       ‘lasterr’              4.0.0
‘error_text’           ‘lasterr’              4.0.0
‘polyderiv’            ‘polyder’              4.0.0
‘shell_cmd’            ‘system’               4.0.0
‘studentize’           ‘zscore’               4.0.0
‘sylvester_matrix’     ‘hadamard (2^k)’       4.0.0
‘default_save_options’ ‘save_default_options’ 4.2.0
‘gen_doc_cache’        ‘doc_cache_create’     4.2.0
‘interp1q’             ‘interp1’              4.2.0
‘isequalwithequalnans’ ‘isequaln’             4.2.0
‘java_convert_matrix’  ‘java_matrix_autoconversion’4.2.0
‘java_debug’           ‘debug_java’           4.2.0
‘java_invoke’          ‘javaMethod’           4.2.0
‘java_new’             ‘javaObject’           4.2.0
‘java_unsigned_conversion’‘java_unsigned_autoconversion’4.2.0
‘javafields’           ‘fieldnames’           4.2.0
‘javamethods’          ‘methods’              4.2.0
‘re_read_readline_init_file’‘readline_re_read_init_file’4.2.0
‘read_readline_init_file’‘readline_read_init_file’4.2.0
‘saving_history’       ‘history_save’         4.2.0
‘allow_noninteger_range_as_index’None         4.4.0
‘bicubic’              ‘interp2’              4.4.0
‘delaunay3’            ‘delaunay’             4.4.0
‘do_braindead_shortcircuit_evaluation’None    4.4.0
‘dump_prefs’           ‘’ None 4.4.0
‘find_dir_in_path’     ‘dir_in_loadpath’      4.4.0
‘finite’               ‘isfinite’             4.4.0
‘fmod’                 ‘rem’                  4.4.0
‘fnmatch’              ‘glob’ or ‘regexp’     4.4.0
‘gmap40’               None                   4.4.0
‘loadaudio’            ‘audioread’            4.4.0
‘luinc’                ‘ichol’ or ‘ilu’       4.4.0
‘mouse_wheel_zoom’     ‘mousehweelzoom’       4.4.0
                       property
‘nfields’              ‘numfields’            4.4.0
‘octave_tmp_file_name’ ‘tempname’             4.4.0
‘playaudio’            ‘audioplayer’          4.4.0
‘saveaudio’            ‘audiowrite’           4.4.0
‘setaudio’             None                   4.4.0
‘syl’                  ‘sylvester’            4.4.0
‘usage’                ‘print_usage’          4.4.0
‘bitmax’               ‘flintmax’             5.1.0
‘mahalanobis’          ‘mahal’ in Octave      5.1.0
                       Forge statistics pkg
‘md5sum’               ‘hash’                 5.1.0
‘octave_config_info’   ‘__octave_config_info__’5.1.0
‘onenormest’           ‘normest1’             5.1.0
‘sleep’                ‘pause’                5.1.0
‘usleep’               ‘pause’                5.1.0
‘wavread’              ‘audioread’            5.1.0
‘wavwrite’             ‘audiowrite’           5.1.0


File: octave.info,  Node: Trouble,  Next: Installation,  Prev: Obsolete Functions,  Up: Top

Appendix D Known Causes of Trouble
**********************************

This section describes known problems that affect users of Octave.  Most
of these are not Octave bugs per se—if they were, we would fix them.
But the result for a user may be like the result of a bug.

   Some of these problems are due to bugs in other software, some are
missing features that are too much work to add, and some are places
where people’s opinions differ as to what is best.

* Menu:

* Actual Bugs::                 Bugs we will fix later.
* Reporting Bugs::
* How To Get Help with Octave::
* How to Distinguish Between Octave and Matlab::


File: octave.info,  Node: Actual Bugs,  Next: Reporting Bugs,  Up: Trouble

D.1 Actual Bugs We Haven’t Fixed Yet
====================================

   • Output that comes directly from Fortran functions is not sent
     through the pager and may appear out of sequence with other output
     that is sent through the pager.  One way to avoid this is to force
     pending output to be flushed before calling a function that will
     produce output from within Fortran functions.  To do this, use the
     command

          fflush (stdout)

     Another possible workaround is to use the command

          page_screen_output (false);

     to turn the pager off.

   A list of ideas for future enhancements is distributed with Octave.
See the file ‘PROJECTS’ in the top level directory in the source
distribution.


File: octave.info,  Node: Reporting Bugs,  Next: How To Get Help with Octave,  Prev: Actual Bugs,  Up: Trouble

D.2 Reporting Bugs
==================

Your bug reports play an essential role in making Octave reliable.

   When you encounter a problem, the first thing to do is to see if it
is already known.  *Note Trouble::.  If it isn’t known, then you should
report the problem.

   Reporting a bug may help you by bringing a solution to your problem,
or it may not.  In any case, the principal function of a bug report is
to help the entire community by making the next version of Octave work
better.  Bug reports are your contribution to the maintenance of Octave.

   In order for a bug report to serve its purpose, you must include the
information that makes it possible to fix the bug.

* Menu:

* Bug Criteria::
* Bug Tracker::        Where to submit your bug report.
* Bug Reporting::      How to report a bug effectively.
* Sending Patches::    How to send a patch for Octave.


File: octave.info,  Node: Bug Criteria,  Next: Bug Tracker,  Up: Reporting Bugs

D.2.1 Have You Found a Bug?
---------------------------

If you are not sure whether you have found a bug, here are some
guidelines:

   • If Octave gets a fatal signal, for any input whatever, that is a
     bug.  Reliable interpreters never crash.

   • If Octave produces incorrect results, for any input whatever, that
     is a bug.

   • Some output may appear to be incorrect when it is in fact due to a
     program whose behavior is undefined, which happened by chance to
     give the desired results on another system.  For example, the range
     operator may produce different results because of differences in
     the way floating point arithmetic is handled on various systems.

   • If Octave produces an error message for valid input, that is a bug.

   • If Octave does not produce an error message for invalid input, that
     is a bug.  However, you should note that your idea of “invalid
     input” might be my idea of “an extension” or “support for
     traditional practice”.

   • If you are an experienced user of programs like Octave, your
     suggestions for improvement are welcome in any case.


File: octave.info,  Node: Bug Tracker,  Next: Bug Reporting,  Prev: Bug Criteria,  Up: Reporting Bugs

D.2.2 Where to Report Bugs
--------------------------

To report a bug in Octave, submit a bug report to the Octave bug tracker
<https://bugs.octave.org>.

   *Do not send bug reports to ‘help-octave’*.  Most users of Octave do
not want to receive bug reports.


File: octave.info,  Node: Bug Reporting,  Next: Sending Patches,  Prev: Bug Tracker,  Up: Reporting Bugs

D.2.3 How to Report Bugs
------------------------

Submit bug reports for Octave to the Octave bug tracker
<https://bugs.octave.org>.

   The fundamental principle of reporting bugs usefully is this: *report
all the facts*.  If you are not sure whether to state a fact or leave it
out, state it!

   Often people omit facts because they think they know what causes the
problem and they conclude that some details don’t matter.  Thus, you
might assume that the name of the variable you use in an example does
not matter.  Well, probably it doesn’t, but one cannot be sure.  Perhaps
the bug is a stray memory reference which happens to fetch from the
location where that name is stored in memory; perhaps, if the name were
different, the contents of that location would fool the interpreter into
doing the right thing despite the bug.  Play it safe and give a
specific, complete example.

   Keep in mind that the purpose of a bug report is to enable someone to
fix the bug if it is not known.  Always write your bug reports on the
assumption that the bug is not known.

   Sometimes people give a few sketchy facts and ask, “Does this ring a
bell?” This cannot help us fix a bug.  It is better to send a complete
bug report to begin with.

   Try to make your bug report self-contained.  If we have to ask you
for more information, it is best if you include all the previous
information in your response, as well as the information that was
missing.

   To enable someone to investigate the bug, you should include all
these things:

   • The version of Octave.  You can get this by noting the version
     number that is printed when Octave starts, or running it with the
     ‘-v’ option.

   • A complete input file that will reproduce the bug.

     A single statement may not be enough of an example—the bug might
     depend on other details that are missing from the single statement
     where the error finally occurs.

   • The command arguments you gave Octave to execute that example and
     observe the bug.  To guarantee you won’t omit something important,
     list all the options.

     If we were to try to guess the arguments, we would probably guess
     wrong and then we would not encounter the bug.

   • The type of machine you are using, and the operating system name
     and version number.

   • The command-line arguments you gave to the ‘configure’ command when
     you installed the interpreter.

   • A complete list of any modifications you have made to the
     interpreter source.

     Be precise about these changes—show a context diff for them.

   • Details of any other deviations from the standard procedure for
     installing Octave.

   • A description of what behavior you observe that you believe is
     incorrect.  For example, "The interpreter gets a fatal signal," or,
     "The output produced at line 208 is incorrect."

     Of course, if the bug is that the interpreter gets a fatal signal,
     then one can’t miss it.  But if the bug is incorrect output, we
     might not notice unless it is glaringly wrong.

     Even if the problem you experience is a fatal signal, you should
     still say so explicitly.  Suppose something strange is going on,
     such as, your copy of the interpreter is out of sync, or you have
     encountered a bug in the C library on your system.  Your copy might
     crash and the copy here would not.  If you said to expect a crash,
     then when the interpreter here fails to crash, we would know that
     the bug was not happening.  If you don’t say to expect a crash,
     then we would not know whether the bug was happening.  We would not
     be able to draw any conclusion from our observations.

     Often the observed symptom is incorrect output when your program is
     run.  Unfortunately, this is not enough information unless the
     program is short and simple.  It is very helpful if you can include
     an explanation of the expected output, and why the actual output is
     incorrect.

   • If you wish to suggest changes to the Octave source, send them as
     context diffs.  If you even discuss something in the Octave source,
     refer to it by context, not by line number, because the line
     numbers in the development sources probably won’t match those in
     your sources.

   Here are some things that are not necessary:

   • A description of the envelope of the bug.

     Often people who encounter a bug spend a lot of time investigating
     which changes to the input file will make the bug go away and which
     changes will not affect it.  Such information is usually not
     necessary to enable us to fix bugs in Octave, but if you can find a
     simpler example to report _instead_ of the original one, that is a
     convenience.  Errors in the output will be easier to spot, running
     under the debugger will take less time, etc.  Most Octave bugs
     involve just one function, so the most straightforward way to
     simplify an example is to delete all the function definitions
     except the one in which the bug occurs.

     However, simplification is not vital; if you don’t want to do this,
     report the bug anyway and send the entire test case you used.

   • A patch for the bug.  Patches can be helpful, but if you find a
     bug, you should report it, even if you cannot send a fix for the
     problem.


File: octave.info,  Node: Sending Patches,  Prev: Bug Reporting,  Up: Reporting Bugs

D.2.4 Sending Patches for Octave
--------------------------------

If you would like to write bug fixes or improvements for Octave, that is
very helpful.  When you send your changes, please follow these
guidelines to avoid causing extra work for us in studying the patches.

   If you don’t follow these guidelines, your information might still be
useful, but using it will take extra work.  Maintaining Octave is a lot
of work in the best of circumstances, and we can’t keep up unless you do
your best to help.

   • Send an explanation with your changes of what problem they fix or
     what improvement they bring about.  For a bug fix, just include a
     copy of the bug report, and explain why the change fixes the bug.

   • Always include a proper bug report for the problem you think you
     have fixed.  We need to convince ourselves that the change is right
     before installing it.  Even if it is right, we might have trouble
     judging it if we don’t have a way to reproduce the problem.

   • Include all the comments that are appropriate to help people
     reading the source in the future understand why this change was
     needed.

   • Don’t mix together changes made for different reasons.  Send them
     _individually_.

     If you make two changes for separate reasons, then we might not
     want to install them both.  We might want to install just one.

   • Use ‘diff -c’ to make your diffs.  Diffs without context are hard
     for us to install reliably.  More than that, they make it hard for
     us to study the diffs to decide whether we want to install them.
     Unified diff format is better than contextless diffs, but not as
     easy to read as ‘-c’ format.

     If you have GNU diff, use ‘diff -cp’, which shows the name of the
     function that each change occurs in.

   • Write the change log entries for your changes.

     Read the ‘ChangeLog’ file to see what sorts of information to put
     in, and to learn the style that we use.  The purpose of the change
     log is to show people where to find what was changed.  So you need
     to be specific about what functions you changed; in large
     functions, it’s often helpful to indicate where within the function
     the change was made.

     On the other hand, once you have shown people where to find the
     change, you need not explain its purpose.  Thus, if you add a new
     function, all you need to say about it is that it is new.  If you
     feel that the purpose needs explaining, it probably does—but the
     explanation will be much more useful if you put it in comments in
     the code.

     If you would like your name to appear in the header line for who
     made the change, send us the header line.


File: octave.info,  Node: How To Get Help with Octave,  Next: How to Distinguish Between Octave and Matlab,  Prev: Reporting Bugs,  Up: Trouble

D.3 How To Get Help with Octave
===============================

The mailing list <help@octave.org> exists for the discussion of matters
related to using and installing Octave.  If would like to join the
discussion, please send a short note to <help-request@octave.org>.

   *Please do not* send requests to be added or removed from the mailing
list, or other administrative trivia to the list itself.

   If you think you have found a bug in Octave or in the installation
procedure, however, you should submit a complete bug report to the
Octave bug tracker at <https://bugs.octave.org>.  But before you submit
a bug report, please read <https://www.octave.org/bugs.html> to learn
how to submit a useful bug report.


File: octave.info,  Node: How to Distinguish Between Octave and Matlab,  Prev: How To Get Help with Octave,  Up: Trouble

D.4 How to Distinguish Between Octave and Matlab
================================================

Octave and MATLAB are very similar, but handle Java slightly different.
Therefore it may be necessary to detect the environment and use the
appropriate functions.  The following function can be used to detect the
environment.  Due to the persistent variable it can be called repeatedly
without a heavy performance hit.

   Example:

     %%
     %% Return: true if the environment is Octave.
     %%
     function retval = isOctave
       persistent cacheval;  % speeds up repeated calls

       if isempty (cacheval)
         cacheval = (exist ("OCTAVE_VERSION", "builtin") > 0);
       end

       retval = cacheval;
     end


File: octave.info,  Node: Installation,  Next: Grammar and Parser,  Prev: Trouble,  Up: Top

Appendix E Installing Octave
****************************

The procedure for installing Octave from source on a Unix-like system is
described next.  Building on other platforms will follow similar steps.
Note that this description applies to Octave releases.  Building the
development sources from the Mercurial archive requires additional steps
as described in the development source itself.

* Menu:

* Build Dependencies::
* Running Configure and Make::
* Compiling Octave with 64-bit Indexing::
* Installation Problems::


File: octave.info,  Node: Build Dependencies,  Next: Running Configure and Make,  Up: Installation

E.1 Build Dependencies
======================

Octave is a fairly large program with many build dependencies.  You may
be able to find pre-packaged versions of the dependencies distributed as
part of your system, or you may have to build some or all of them
yourself.

* Menu:

* Obtaining the Dependencies Automatically::
* Build Tools::
* External Packages::


File: octave.info,  Node: Obtaining the Dependencies Automatically,  Next: Build Tools,  Up: Build Dependencies

E.1.1 Obtaining the Dependencies Automatically
----------------------------------------------

On some systems you can obtain many of Octave’s build dependencies
automatically.  The commands for doing this vary by system.  Similarly,
the names of pre-compiled packages vary by system and do not always
match exactly the names listed in *note Build Tools:: and *note External
Packages::.

   You will usually need the development version of an external
dependency so that you get the libraries and header files for building
software, not just for running already compiled programs.  These
packages typically have names that end with the suffix ‘-dev’ or
‘-devel’.

   On systems with ‘apt-get’ (Debian, Ubuntu, etc.), you may be able to
install most of the tools and external packages using a command similar
to

     apt-get build-dep octave

The specific package name may be ‘octave3.2’ or ‘octave3.4’.  The set of
required tools and external dependencies does not change frequently, so
it is not important that the version match exactly, but you should use
the most recent one available.

   On systems with ‘yum’ (Fedora, Red Hat, etc.), you may be able to
install most of the tools and external packages using a command similar
to

     yum-builddep octave

The ‘yum-builddep’ utility is part of the ‘yum-utils’ package.

   For either type of system, the package name may include a version
number.  The set of required tools and external dependencies does not
change frequently, so it is not important that the version exactly match
the version you are installing, but you should use the most recent one
available.


File: octave.info,  Node: Build Tools,  Next: External Packages,  Prev: Obtaining the Dependencies Automatically,  Up: Build Dependencies

E.1.2 Build Tools
-----------------

The following tools are required:

C++, C, and Fortran compilers
     The Octave sources are primarily written in C++, but some portions
     are also written in C and Fortran.  The Octave sources are intended
     to be portable.  Recent versions of the GNU compiler collection
     (GCC) should work (<https://gcc.gnu.org>).  If you use GCC, you
     should avoid mixing versions.  For example, be sure that you are
     not using the obsolete ‘g77’ Fortran compiler with modern versions
     of ‘gcc’ and ‘g++’.

GNU Make
     Tool for building software (<https://www.gnu.org/software/make>).
     Octave’s build system requires GNU Make.  Other versions of Make
     will not work.  Fortunately, GNU Make is highly portable and easy
     to install.

AWK, sed, and other Unix utilities
     Basic Unix system utilities are required for building Octave.  All
     will be available with any modern Unix system and also on Windows
     with either Cygwin or MinGW and MSYS.

   Additionally, the following tools may be needed:

Bison
     Parser generator (<https://www.gnu.org/software/bison>).  You will
     need Bison if you modify the ‘oct-parse.yy’ source file or if you
     delete the files that are generated from it.

Flex
     Lexer analyzer (<https://www.gnu.org/software/flex>).  You will
     need Flex if you modify the ‘lex.ll’ source file or if you delete
     the files that are generated from it.

Autoconf
     Package for software configuration
     (<https://www.gnu.org/software/autoconf>).  Autoconf is required if
     you modify Octave’s ‘configure.ac’ file or other files that it
     requires.

Automake
     Package for Makefile generation
     (<https://www.gnu.org/software/automake>).  Automake is required if
     you modify Octave’s ‘Makefile.am’ files or other files that they
     depend on.

Libtool
     Package for building software libraries
     (<https://www.gnu.org/software/libtool>).  Libtool is required by
     Automake.

gperf
     Perfect hash function generator
     (<https://www.gnu.org/software/gperf>).  You will need gperf if you
     modify the ‘octave.gperf’ file or if you delete the file that is
     generated from it.

Texinfo
     Package for generating online and print documentation
     (<https://www.gnu.org/software/texinfo>).  You will need Texinfo to
     build Octave’s documentation or if you modify the documentation
     source files or the docstring of any Octave function.

