Optional option argument with getopts

Question

while getopts \"hd:R:\" arg; do
  case $arg in
    h)
      echo \"usgae\" 
      ;;
    d)
      dir=$OPTARG
      ;;
    R)
      if [[ $OPTARG =~ ^[0-9]+$ ]];then         


        

Answer 1

I just ran into this myself and felt that none of the existing solutions were really clean. After working on it a bit and trying various things, I found that leveraging getopts SILENT mode with :) ... appears to have done the trick along with keeping OPTIND in sync.

---

usage: test.sh [-abst] [-r [DEPTH]] filename
*NOTE: -r (recursive) with no depth given means full recursion

#!/usr/bin/env bash

depth='-d 1'

while getopts ':abr:st' opt; do
    case "${opt}" in
        a) echo a;;
        b) echo b;;
        r) if [[ "${OPTARG}" =~ ^[0-9]+$ ]]; then
               depth="-d ${OPTARG}"
           else
               depth=
               (( OPTIND-- ))
           fi
           ;;
        s) echo s;;
        t) echo t;;
        :) [[ "${OPTARG}" = 'r' ]] && depth=;;
        *) echo >&2 "Invalid option: ${opt}"; exit 1;;
    esac
done
shift $(( OPTIND - 1 ))

filename="$1"
...