Arguments parsing in bash example

isobuilder.sh

#!/bin/bash
#
# This script will extract, modify and repack a bootable iso image.
#
# Features:
#  - Add kickstart file
#  - Add post install kickstart scripts 
#  - Play scripts in a chroot of the filesystem
#
# Dependencies:
#  - mkisofs

# Initialize our own variables:
output="./output.iso"
workdir="~/.cache/isobuilder"
kickstart=""
postscripts=""
scripts=""

function usage {
    echo "Usage: $(basename $0) [OPTION]... isofile.iso"
    echo "  -o       output iso file path (default: $output)"
    echo "  -w       working directory used internally "
    echo "           and cleaned when terminated (default: $workdir)"
    echo "  -k       kickstart file path"
    echo "  -p       post install script to add (can be used multiple times)"
    echo "  -s       script to play in chroot (can be used multiple times)"
    echo "  -h       display help"
}

# The variable OPTIND holds the number of options parsed by the last call to getopts
OPTIND=1         # Reset in case getopts has been used previously in the shell.

while getopts "o:w:k:p:s:h" opt; do
    case "$opt" in
    h|\?)
        usage
        exit 0
        ;;
    :)
        echo "Invalid option: $OPTARG requires an argument"
        exit 0
        ;;
    o)  output=$OPTARG
        ;;
    w)  workdir=$OPTARG
        ;;
    k)  kickstart=$OPTARG
        ;;
    p)  postscripts+=("$OPTARG")
        ;;
    s)  scripts+=("$OPTARG")
        ;;
    esac
done

shift $((OPTIND-1))

# Ignore -- if existing
[ "${1:-}" = "--" ] && shift

# Check positional mandatory arguments
iso=$1
if [ -z "$iso" ]
  then
      usage
      exit 0
fi

echo "iso: $iso"
echo "output: $output"
echo "workdir: $workdir"
echo "kickstart: $kickstart"

# List scripts
for val in "${scripts[@]}"; do
    echo "script: $val"
done

# List post scripts
for val in "${postscripts[@]}"; do
    echo "postscript: $val"
done