Portable getopt argument processing in shell scripts. Detects which version of getopt is installed. When available, it uses GNU enhanced getopt to support long option names and whitespaces in arguments. Otherwise, defaults to using the original getopt.

getopt-example.sh

#!/bin/sh
#
# Example showing use of getopt detection and use of GNU enhanced getopt
# to handle arguments containing whitespace.
#
# Written in 2004 by Hoylen Sue <hoylen@hoylen.com>
#
# To the extent possible under law, the author(s) have dedicated all copyright and
# related and neighboring rights to this software to the public domain worldwide.
# This software is distributed without any warranty.
#
# You should have received a copy of the CC0 Public Domain Dedication along with this software.
# If not, see <http://creativecommons.org/publicdomain/zero/1.0/>.

PROG=`basename $0`
VERSION=0.1

# Remove this trap if you are doing your own error detection or don't care about errors
trap "echo $PROG: error encountered: aborted; exit 3" ERR

#----------------------------------------------------------------
# Process command line arguments

## Define options: trailing colon means has an argument (customize this: 1 of 3)

SHORT_OPTS=o:vh
LONG_OPTS=output:,verbose,version,help

SHORT_HELP="Usage: $PROG [options] arguments
Options:
  -o file  output file name
  -v       show extra information
  -h       show this help message"

LONG_HELP="Usage: $PROG [options] arguments
Options:
  -o | --output file  output file name
  -v | --verbose      show extra information
  -h | --help         show this help message
  --version           show version information"

# Detect if GNU Enhanced getopt is available

HAS_GNU_ENHANCED_GETOPT=
if getopt -T >/dev/null; then :
else
  if [ $? -eq 4 ]; then
    HAS_GNU_ENHANCED_GETOPT=yes
  fi
fi

# Run getopt (runs getopt first in `if` so `trap ERR` does not interfere)

if [ -n "$HAS_GNU_ENHANCED_GETOPT" ]; then
  # Use GNU enhanced getopt
  if ! getopt --name "$PROG" --long $LONG_OPTS --options $SHORT_OPTS -- "$@" >/dev/null; then
    echo "$PROG: usage error (use -h or --help for help)" >&2
    exit 2
  fi
  ARGS=`getopt --name "$PROG" --long $LONG_OPTS --options $SHORT_OPTS -- "$@"`
else
  # Use original getopt (no long option names, no whitespace, no sorting)
  if ! getopt $SHORT_OPTS "$@" >/dev/null; then
    echo "$PROG: usage error (use -h for help)" >&2
    exit 2
  fi    
  ARGS=`getopt $SHORT_OPTS "$@"`
fi
eval set -- $ARGS

## Process parsed options (customize this: 2 of 3)
 
while [ $# -gt 0 ]; do
    case "$1" in
        -o | --output)   OUTFILE="$2"; shift;;
        -v | --verbose)  VERBOSE=yes;;
        -h | --help)     if [ -n "$HAS_GNU_ENHANCED_GETOPT" ]
                         then echo "$LONG_HELP";
                         else echo "$SHORT_HELP";
                         fi;  exit 0;;
        --version)       echo "$PROG $VERSION"; exit 0;;
        --)              shift; break;; # end of options
    esac
    shift
done

## Process remaining arguments and use options (customize this: 3 of 3)

echo "$PROG: DEBUG: option VERBOSE: $VERBOSE"
echo "$PROG: DEBUG: option OUTFILE: $OUTFILE"

if [ $# -gt 0 ]; then
  for ARG in "$@"; do
    echo "$PROG: DEBUG: argument: $ARG"
  done
fi

#EOF