bash - passing optional arguments to script - parametername + string_value - bash

Question

i use a script that accepts parameter. parameters are optional and may occur in any order.
#!/bin/bash
# script name: test.sh
for var in "$#"
do
if [ ! -z "$var" ] && ([ $var = "--example" ] || [ $var = "-e" ]); then
echo "example"
elif [ ! -z "$var" ] && ([ $var = "--project" ] || [ $var = "-p" ]); then
echo "project with string xxxxxxx"
fi
done
in this simple example, you could call it like follows (some examples):
# this will echo example
./test.sh --example
# this will echo project with string xxxxxxx
./test.sh --project
# this will echo both example and project with string xxxxxxx
./test.sh --example --project
NOW, what i want to achieve is that i can do something like this (warning, this is pseuco code):
#!/bin/bash
# script name: test.sh
for var in "$#"
do
if [ ! -z "$var" ] && ([ $var = "--example" ] || [ $var = "-e" ]); then
echo "example"
elif [ ! -z "$var" ] && ([ $var = "--project" ] || [ $var = "-p" ]); then
echo "project with string $VAR_VALUE"
fi
done
# this will echo example
./test.sh --example
# this will echo project with string myproject1
./test.sh --project="myproject1"
# this will echo both example and project with string myproject2
./test.sh --example --project="myproject2"
can someone help me rewrite it so this will work somehow?

Answer 1

Use getopt. It handles short and long options, allows for both --long value and --long=value, decomposes -abc into -a -b -c, understands -- to end option parsing, and more.
#!/bin/bash
args=$(getopt -o ep: -l example,project: -n "$0" -- "$#") || exit
eval set -- "$args"
while [[ $1 != '--' ]]; do
case "$1" in
-e|--example) echo "example"; shift 1;;
-p|--project) echo "project = $2"; shift 2;;
# shouldn't happen unless we're missing a case
*) echo "unhandled option: $1" >&2; exit 1;;
esac
done
shift # skip '--'
echo "remaining non-option arguments: $#"

Answer 2

There are two possible path toward parsing argument list
Build custom option parser
use getopt, using 'long options'
The first approach is relatively simple (at this time). Using case instead of if to handle variants:
last_arg=
for arg in "$#"
do
if [ "$last_arg" = "-p" ] ; then
VAR_VALUE=$arg ;
last_arg=
echo "project with string $VAR_VALUE"
continue
fi
case "$arg" in
-e | --example)
echo "example" ;;
-p)
last_arg=$arg ;;
--project=*)
VAR_VALUE=${arg#*=}
echo "project with string $VAR_VALUE" ;;
*) ERROR-MESSAGE ;;
esac
done
exit
The BETTER approach is to leverage existing code. In particular getopt, which can handle long options:
#! /bin/bash
if T=$(getopt -o ep: --long 'example,project:' -n ${0#*/} -- "$#") ; then
eval set -- "$T"
else
exit $?
fi
while [ "$#" -gt 0 ] ; do
case "$1" in
-e | --example)
echo "example"
;;
-p | --project)
shift
VAR_VALUE=$1
echo "project with string $VAR_VALUE"
;;
--)
break
;;
*) echo "ERROR:$1" ;;
esac
shift
done