If you're interested in helping, here are some tasks that we've considered
over the years.  Beware: some are quite old and no longer valid.  To avoid
wasting your time by duplicating work or by working on a task that is no
longer pertinent, please search the mailing list and post your intent
before embarking on a big project.

==================================================
Modify chmod so that it does not change an inode's st_ctime
  when the selected operation would have no other effect.
  First suggested by Hans Ecke <https://hans.ecke.ws> in
    https://lists.gnu.org/r/bug-coreutils/2004-09/msg00145.html
  Discussed more recently on <https://bugs.debian.org/497514>.

Suggestion from Paul Eggert:
  More generally, there's not that much use for imaxtostr nowadays,
  since the inttypes module and newer versions of gettext allow things
  like _("truncating %s at %jd bytes") to work portably.
  I suspect that (if someone cares to take the time) we can remove
  all instances of imaxtostr and umaxtostr in coreutils and gnulib.

cp --recursive: use fts and *at functions to perform directory traversals
  in source and destination hierarchy rather than forming full file names.
  The latter (current) approach fails unnecessarily when the names
  become very long, and requires space and time that is quadratic in the
  depth of the hierarchy.  [Bo Borgerson is working on this]

printf:
  Now that gnulib supports *printf("%a"), import one of the
  *printf-posix modules so that printf(1) will support %a even on
  platforms where the native *printf(3) is deficient.
  Suggestion from Eric Blake.

consider adding some implementation of the "col" utility
  Suggested by Karl Berry.

doc/coreutils.texi:
  Address this comment: FIXME: mv's behavior in this case is system-dependent
  Better still: fix the code so it's *not* system-dependent.

ls: add --format=FORMAT option that controls how each line is printed.

copy.c: Address the FIXME-maybe comment in copy_internal.
And once that's done, add an exclusion so that 'cp --link'
no longer incurs the overhead of saving src. dev/ino and dest. filename
in the hash table.

Write an autoconf test to work around build failure in HPUX's 64-bit mode.
See notes in README-install -- and remove them once there's a work-around.

Integrate use of sendfile, suggested here:
  https://lists.gnu.org/r/bug-fileutils/2003-03/msg00030.html
I don't plan to do that, since a few tests demonstrate no significant benefit.

printf: consider adapting builtins/printf.def from bash

tail: don't use xlseek; it *exits*.
  Instead, maybe use a macro and return nonzero.

tr: support nontrivial equivalence classes, e.g. [=e=] with LC_COLLATE=fr_FR

lib/strftime.c: Since %N is the only format that we need but that
  glibc's strftime doesn't support, consider using a wrapper that
  would expand /%(-_)?\d*N/ to the desired string and then pass the
  resulting string to glibc's strftime.

sort: Investigate better sorting algorithms; see Knuth vol. 3.

  We tried list merge sort, but it was about 50% slower than the
  recursive algorithm currently used by sortlines, and it used more
  comparisons.  We're not sure why this was, as the theory suggests it
  should do fewer comparisons, so perhaps this should be revisited.
  List merge sort was implemented in the style of Knuth algorithm
  5.2.4L, with the optimization suggested by exercise 5.2.4-22.  The
  test case was 140,213,394 bytes, 426,4424 lines, text taken from the
  GCC 3.3 distribution, sort.c compiled with GCC 2.95.4 and running on
  Debian 3.0r1 GNU/Linux, 2.4GHz Pentium 4, single pass with no
  temporary files and plenty of RAM.

  Since comparisons seem to be the bottleneck, perhaps the best
  algorithm to try next should be merge insertion.  See Knuth section
  5.3.1, who credits Lester Ford, Jr. and Selmer Johnson, American
  Mathematical Monthly 66 (1959), 387-389.

shred: Update shred as described here to conform to DoD 5220 rules:
https://lists.gnu.org/r/bug-coreutils/2007-05/msg00075.html

Remove suspicious uses of alloca (ones that may allocate more than
   about 4k)

Improve test coverage.
  See HACKING for instructions on generating an html test coverage report.
  Find a program that has poor coverage and improve.

Changes expected to go in, someday.
======================================

  dd patch from Olivier Delhomme

  test/mv/*: clean up $other_partition_tmpdir in all cases

  ls: when both -l and --dereference-command-line-symlink-to-dir are
  specified, consider whether to let the latter select whether to
  dereference command line symlinks to directories.  Since -l has
  an implicit --NO-dereference-command-line-symlink-to-dir meaning.
  Pointed out by Karl Berry.

  Pending copyright papers:
  ------------------------
  getpwnam from Bruce Korb

  pb (progress bar) from Miika Pekkarinen

  ------------------------------

Remove long-deprecated options.  Search case-insensitive for
'deprecated' and 'remove in '.  Automate this.

Add a distcheck-time test to ensure that every distributed
file is either read-only(indicating generated) or is
version-controlled and up to date.

remove all uses of the 'register' keyword: Done.  add a maint.mk rule
  for this, too.

remove or adjust chown's --changes option, since it
  can't always do what it currently says it does.

Support arbitrary-precision arithmetic in those tools for which it
makes sense.  Factor and expr already support this via libgmp.
The "test" program is covered via its string-based comparison of
integers.  To be converted: seq.

Adapt tools like wc, tr, fmt, etc. (most of the textutils) to be
  multibyte aware.  The problem is that I want to avoid duplicating
  significant blocks of logic, yet I also want to incur only minimal
  (preferably 'no') cost when operating in single-byte mode.

pr's use of nstrftime can make it malloc a very large (up to SIZE_MAX) buffer

-----

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