I\'d like to use getopts
inside a function that I have defined in my .bash_profile.
The idea is I\'d like to pass in some flags to this function to alter its be
Here is simple example of getopts usage within shell function:
#!/usr/bin/env bash
t() {
local OPTIND
getopts "a:" OPTION
echo Input: $*, OPTION: $OPTION, OPTARG: $OPTARG
}
t "$@"
t -a foo
Output:
$ ./test.sh -a bc
Input: -a bc, OPTION: a, OPTARG: bc
Input: -a foo, OPTION: a, OPTARG: foo
As @Adrian pointed out, local OPTIND
(or OPTIND=1
) needs to be set as shell does not reset OPTIND
automatically between multiple calls to getopts (man bash
).
The base-syntax for getopts
is:
getopts OPTSTRING VARNAME [ARGS...]
and by default, not specifying arguments is equivalent to explicitly calling it with "$@" which is: getopts "a:" opts "$@"
.
In case of problems, these are the used variables for getopts
to check:
OPTIND
- the index to the next argument to be processed,OPTARG
- variable is set to any argument for an option found by getopts
,OPTERR
(not POSIX) - set to 0 or 1 to indicate if Bash should display error messages generated by the getopts
.Further more, see: Small getopts tutorial at The Bash Hackers Wiki
As @Ansgar points out, the argument to your option is stored in ${OPTARG}
, but this is not the only thing to watch out for when using getopts
inside a function. You also need to make sure that ${OPTIND}
is local to the function by either unsetting it or declaring it local
, otherwise you will encounter unexpected behaviour when invoking the function multiple times.
t.sh
:
#!/bin/bash
foo()
{
foo_usage() { echo "foo: [-a <arg>]" 1>&2; exit; }
local OPTIND o a
while getopts ":a:" o; do
case "${o}" in
a)
a="${OPTARG}"
;;
*)
foo_usage
;;
esac
done
shift $((OPTIND-1))
echo "a: [${a}], non-option arguments: $*"
}
foo
foo -a bc bar quux
foo -x
Example run:
$ ./t.sh
a: [], non-option arguments:
a: [bc], non-option arguments: bar quux
foo: [-a <arg>]
If you comment out # local OPTIND
, this is what you get instead:
$ ./t.sh
a: [], non-option arguments:
a: [bc], non-option arguments: bar quux
a: [bc], non-option arguments:
Other than that, its usage is the same as when used outside of a function.
The argument is stored in the varable $OPTARG
.
function t() {
echo $*
getopts "a:" OPTION
echo $OPTION
echo $OPTARG
}
Output:
$ t -a bc
-a bc
a
bc