Argument is empty using getopts

Question

I want to be able to run a script like run.sh test -a but my arguments are empty.

#!/bin/bash

function install() {
    echo "Installing $1"
}

while getopts "ab" ARG; do
  case "$ARG" in
    a) install
       echo "Setting up A" ;;
    b) install
       echo "Setting up B" ;;
    *) echo "argument missing" ;;
  esac
done

My expected output would be if I run run.sh test -a:

Installing test
Setting up A

However there is no output returned. If I run run.sh -a, I get:

Installing
Setting up A

Does this answer your question? [An example of how to use getopts in bash](https://stackoverflow.com/questions/16483119/an-example-of-how-to-use-getopts-in-bash) — Antonio Petricca, Mar 29 '22 at 15:24
That is odd, the output should be `Installing` without anything after in both cases. — KamilCuk, Mar 29 '22 at 15:29
You can't access the shell positional parameters from inside a function; the function's own positional parameters shadows them. — chepner, Mar 29 '22 at 15:43
@AntonioPetricca The linked question confuses getopt (program) with getopts (builtin) — stark, Mar 29 '22 at 15:49

score 0 · Answer 1 · answered Mar 29 '22 at 16:37

Probably not the most elegant way but I got it sort of working by using the second argument instead.

Ended up reworking it like so:

install=$2

function install() {
    echo "Installing $install"
}

while getopts "ab" ARG; do
  case "$ARG" in
    a) install
       echo "Setting up A" ;;
    b) install
       echo "Setting up B" ;;
    *) echo "argument missing" ;;
  esac
done

So I running run.sh -a test would return:

Installing test
Setting up A

score 0 · Answer 2 · answered Mar 30 '22 at 05:16

0

getopts does not allow you to specify the options after the non-option arguments. This is a general principle of many Unix tools, though some have deviated.

answered Mar 30 '22 at 05:16

tripleee

175,061
34
275
318

I'm inclined to guess that Windows has persuaded some users that this is a good idea, which should immediately tell you that it's not. – tripleee Mar 30 '22 at 05:16

Argument is empty using getopts

2 Answers2