|GETOPT(1)||General Commands Manual||GETOPT(1)|
getoptis 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 whitespace. However, if a letter is followed by two colons, the argument is optional and may not be separated by whitespace - this is an extension not covered by POSIX. The special option ‘--’ is used to delimit the end of the options.
getoptwill 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.
-b, and the option
-o, which requires an argument.
args=`getopt abo: $*` if [ $? -ne 0 ] then echo 'Usage: ...' exit 2 fi set -- $args while [ $# -ne 0 ] do case "$1" in -a|-b) flag="$1"; shift;; -o) oarg="$2"; shift; shift;; --) shift; break;; esac done
This code will accept any of the following as equivalent:
cmd -aoarg file file cmd -a -o arg file file cmd -oarg -a file file cmd -a -oarg -- file file
getoptprints an error message on the standard error output when it encounters an option letter not included in optstring.
set -- `getopt optstring $*`
is not recommended, as the exit value from set
will prevent the exit value from
getopt from being
Arguments containing whitespace 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
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.
|March 16, 2018||OpenBSD-current|