.Nd parse command options
.Nm set \-\- \`getopt optstring $*\`
is used to break up options in command lines for easy parsing by
shell procedures, and to check for legal options.
is a string of recognized option letters (see
if a letter is followed by a colon, the option
is expected to have an argument which may or may not be
separated from it by white space.
is used to delimit the end of the options.
in the arguments at the end of the options,
or recognize it if used explicitly.
(\fB$1 $2\fR ...) are reset so that each option is
and in its own shell argument;
each option argument is also in its own shell argument.
The following code fragment shows how one might process the arguments
for a command that can take the options
which requires an argument.
.Bd -literal -offset indent
set \-\- \`getopt abo: $*\`
This code will accept any of the following as equivalent:
.Bd -literal -offset indent
cmd \-a \-o arg file file
cmd \-a \-oarg \-\- file file
prints an error message on the standard error output when it
encounters an option letter not included in
Written by Henry Spencer, working from a Bell Labs manual page.
Behavior believed identical to the Bell version.
Arguments containing white space or imbedded shell metacharacters
generally will not survive intact; this looks easy to fix but isn't.
The error message for an invalid option is identified as coming
rather than from the shell procedure containing the invocation
this again is hard to fix.
The precise best way to use the
command to set the arguments without disrupting the value(s) of
shell options varies from one shell version to another.