bashCmdLineParser.sh

#!/bin/bash

usage() {
   echo;
   echo "Description here."
   echo
   echo "Usage:  $0 [options] <arg1> "
   echo
   echo "  <arg1>   Arg1 blah blah"
   echo
   echo "Options:"
   echo
   echo "  --alpha <target>      Alpha blah blah."
   echo "  -h, --help            Prints usage. "
   echo "  -z, --zeta            Zeta blah blah."
   echo
   exit 1;
}

alphaTarget=""
arg1=""
zeta=false

# Parse command line
POSITIONAL=()
while [ $# -gt 0 ]; do
    case $1 in
      --alpha) alphaTarget=$2 ; shift ;;
      -h|--help) usage ;;
      -z|--zeta) zeta=true ;;
      --) break ;;
      -*|--*) echo "$0: ERROR - unrecognized option $1" 1>&2; usage ;;
      *) POSITIONAL+=("$1") ;;
    esac
    shift
done
set -- "${POSITIONAL[@]}"
if [[ $# -ne 1 ]]; then
    echo "$0: Missing <arg1>."
    usage
fi
arg1=$1