NAME
getopt
—
parse command options
SYNOPSIS
args=`getopt optstring $*`
set -- `getopt optstring $*`
DESCRIPTION
getopt
is used to break up options in command lines for
easy parsing by shell procedures, and to check for legal options. [Optstring]
is a string of recognized option letters (see
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 “--” is used to delimit the end of the
options. getopt
will place “--” 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
“-” and in its own shell argument; each option argument is also
in its own shell argument.
getopt
should not be used in new scripts;
use the shell builtin getopts
instead.
EXAMPLES
The following code fragment shows how one might process the arguments for a command that can take the options [a] and [b], and the option [c], which requires an argument.
args=`getopt abc: $*` if [ $? -ne 0 ]; then echo 'Usage: ...' exit 2 fi set -- $args while [ $# -gt 0 ]; do case "$1" in -a|-b) flag=$1 ;; -c) carg=$2; shift ;; --) shift; break ;; esac shift done
This code will accept any of the following as equivalent:
cmd -acarg file file cmd -a -c arg file file cmd -carg -a file file cmd -a -carg -- file file
IEEE Std 1003.2 (“POSIX.2”)
mandates that the sh(1) set command return the value of 0 for the exit status.
Therefore, the exit status of the getopt
command is
lost when getopt
and the
sh(1)
set command are used on the same line. The example given is one way to
detect errors found by getopt
.
DIAGNOSTICS
getopt
prints an error message on the
standard error output when it encounters an option letter not included in
[optstring].
SEE ALSO
HISTORY
Written by Henry Spencer, working from a Bell Labs manual page. Behavior believed identical to the Bell version.
BUGS
Whatever getopt(3) has.
Arguments containing white space or embedded 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
from getopt
rather than from the shell procedure
containing the invocation of getopt
; this again is
hard to fix.
The precise best way to use the set
command to set the arguments without disrupting the value(s) of shell
options varies from one shell version to another.