GETOPT(1) | General Commands Manual | GETOPT(1) |
getopt
— parse
command options
args=`getopt optstring $*`
set -- `getopt optstring $*`
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.
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
.
getopt
prints an error message on the
standard error output when it encounters an option letter not included in
[optstring].
Written by Henry Spencer, working from a Bell Labs manual page. Behavior believed identical to the Bell version.
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.
November 28, 2009 | NetBSD 10.99 |