[jolmg]

To expand on that pattern:

    while (( $# )); do
      case "$1" in
        -h|--help)
          usage
          exit
          ;;

        -v|--version)
          do_version
          exit
          ;;

        -d|--debug)
          debug=true
          ;;

        -a|--arg)
          arg_value="$2"
          shift
          ;;

        *)
          if [[ ! -v pos1 ]]; then
            pos1="$1"
          elif [[ ! -v pos2 ]]; then
            pos2="$1"
          else
            >&2 printf "%s: unrecognized argument\n" "$1"
            >&2 usage
            exit 1
          fi
      esac

      shift
    done

[bewuethr]

The one downside of this is that it doesn't handle squeezing flags as in

    foo -da bar

whereas getopts does. On the other hand, with (the Bash built-in) getopts you're limited to single character flags.

[Spivak]

You can do that it will just make things a little less pretty.

    while (( $# )); do
        case "$1" in
            -*h*|--help)
                do_help
                exit
                ;;
            -*v*|--version)
                do_version
                exit
                ;;
            -*d*|--debug)
                debug=true
                ;;&
            -*a*|--arg)
                value="$2"
                shift
                ;;&
        esac
        shift
    done

It doesn't support args of the form -avalue but those a pretty uncommon anyway.

[jolmg]

That wouldn't work in the general case. Those patterns would also match long options. If I add a case pattern `--all)`, and I call the script with `--all`, it's also going to match

  -*a*|--arg)

You could fix that with:

  -a*|-[!-]*a*|--arg)

> It doesn't support args of the form -avalue but those a pretty uncommon anyway.

You could

  -a*|-[!-]*a*|--arg)
    if [[ "$1" != --arg ]]; then
      value="${1#*a}"
    fi
    if [[ ! "$value" ]]; then
      value="$2"
      shift
    fi
  ;;&

Putting the option stuck together to its value has the advantage of working nicely with brace expansion. For example, you can call `strace -p{1111,2222,3333}` to trace those 3 pids and avoid having to type `-p` 3 times.

[jolmg]

As a final addendum, case clauses of options that take arguments like -a/--arg should not be terminated with `;;&`, but rather with `;;`.

[Spivak]

This is awesome! Thank you for being a total bash nerd.

[jolmg]

There's still one problem. To exemplify it, if you call with `-av`, it'll process the `v` as the option `-v` instead of the option value to `-a`. If you only have one possible option that takes a value, this can be fixed by putting its case clause before all others. If you have more, then that'll require things to get a little more complicated:

      -d*|-[!-]*d*|--debug)
        if [[ ! "$finished_case" && ("$1" = --debug || "$1" =~ '^[^ad]*d') ]]; then
          debug=true
        fi
      ;;&

      -a*|-[!-]*a*|--arg)
        if [[ ! "$finished_case" && ("$1" = --arg || "$1" =~ '^[^a]*a') ]]; then
          if [[ "$1" != --arg ]]; then
            value="${1#*a}"
          fi
          if [[ ! "$value" ]]; then
            value="$2"
            shift
          fi
          finished_case=true
        fi
      ;;&
      ...
    esac

    shift
    finished_case=
  done

All case-clauses would need to use `;;&` by the way, including `-v` and `-h`. The regex is generally:

  "^[^${all_options_with_values}${current_option}]*${current_option}"

Another problem is that option and argument non-recognition would not work as previously layed out. You can include short options that aren't recognized, and they'll be ignored instead of raising errors. For positional arguments, one would need a condition to check for options, since using `;;&` for everything means that everything would land to

  *)

Maybe those are the last issues, but this is already out of hand for otherwise small and simple shell scripts. All these complications arise from trying to support the sticking together of short options and their possible values. Processing arguments in a case loop is much, much simpler if we avoid supporting those 2 features.