exec [ -cl ] [ -a argv0 ] [ command [ arg ... ] ]
       Replace  the  current shell with an external command rather than
       forking.  With -c clear the environment; with -l  prepend  -  to
       the  argv[0] string of the command executed (to simulate a login
       shell); with -a argv0 set the argv[0] string of the command exe-
       cuted.  See the section `Precommand Modifiers' in zshmisc(1).

       If  command  is omitted but any redirections are specified, then
       the redirections will take effect in the current shell.
