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getopt.1 revision 1.6 
 $NetBSD: getopt.1,v 1.6 1997/01/09 20:19:46 tls Exp $
.Dd June 21, 1993
.Dt GETOPT 1
.Os
.Sh NAME
.Nm getopt
.Nd parse command options
.Sh SYNOPSIS
.Nm set -- \`getopt optstring $*\`
.Sh DESCRIPTION
.Nm Getopt
is used to break up options in command lines for easy parsing by
shell procedures, and to check for legal options.
.Op Optstring
is a string of recognized option letters (see
.Xr getopt 3
);
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.
The special option
.Dq --
is used to delimit the end of the options.
.Nm Getopt
will place
.Dq --
in the arguments at the end of the options,
or recognize it if used explicitly.
The shell arguments
($1 $2 ...) are reset so that each option is
preceded by a
.Dq -
and in its own shell argument;
each option argument is also in its own shell argument.
.Sh EXAMPLE
The following code fragment shows how one might process the arguments
for a command that can take the options
.Op a
and
.Op b ,
and the option
.Op o ,
which requires an argument.

p
d -literal -offset indent set -- \`getopt abo: $*\`
if test $? != 0
then
 echo 'Usage: ...'
 exit 2
fi
for i
do
 case "$i"
 in
 -a|-b)
 flag=$i; shift;;
 -o)
 oarg=$2; shift; shift;;
 --)
 shift; break;;
 esac
done
.Ed

p
This code will accept any of the following as equivalent:

p
d -literal -offset indent cmd -aoarg file file
cmd -a -o arg file file
cmd -oarg -a file file
cmd -a -oarg -- file file
.Ed
.Sh SEE ALSO
.Xr sh 1 ,
.Xr getopt 3
.Sh DIAGNOSTICS
.Nm Getopt
prints an error message on the standard error output when it
encounters an option letter not included in
.Op optstring .
.Sh HISTORY
Written by Henry Spencer, working from a Bell Labs manual page.
Behavior believed identical to the Bell version.
.Sh BUGS
Whatever
.Xr getopt 3
has.

p
Arguments containing white space or embedded shell metacharacters
generally will not survive intact; this looks easy to fix but isn't.

p
The error message for an invalid option is identified as coming
from
.Nm getopt
rather than from the shell procedure containing the invocation
of
.Nm getopt ;
this again is hard to fix.

p
The precise best way to use the
.Nm set
command to set the arguments without disrupting the value(s) of
shell options varies from one shell version to another.