NAME
getopt
—
parse command options
SYNOPSIS
args=`getopt optstring $*`; set -- $args |
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
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. 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.
Note that the construction set -- `getopt
optstring $*`
is not recommended, as the exit value from
“set” will prevent the exit value from
getopt
from being determined.
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 -o
,
which requires an argument.
args=`getopt abo: $*` if [ $? -ne 0 ] then echo 'Usage: ...' exit 2 fi set -- $args while [ $# -ge 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
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 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
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.