Example of how to parse options with bash/getopt

parse-options.sh

#!/bin/bash
#
# Example of how to parse short/long options with 'getopt'
#

OPTS=`getopt -o vhns: --long verbose,dry-run,help,stack-size: -n 'parse-options' -- "$@"`

if [ $? != 0 ] ; then echo "Failed parsing options." >&2 ; exit 1 ; fi

echo "$OPTS"
eval set -- "$OPTS"

VERBOSE=false
HELP=false
DRY_RUN=false
STACK_SIZE=0

while true; do
  case "$1" in
    -v | --verbose ) VERBOSE=true; shift ;;
    -h | --help )    HELP=true; shift ;;
    -n | --dry-run ) DRY_RUN=true; shift ;;
    -s | --stack-size ) STACK_SIZE="$2"; shift; shift ;;
    -- ) shift; break ;;
    * ) break ;;
  esac
done

echo VERBOSE=$VERBOSE
echo HELP=$HELP
echo DRY_RUN=$DRY_RUN
echo STACK_SIZE=$STACK_SIZE

@aceeric, if you handle each case correctly, that should never happen. For example, if you omit the -s | --stack-size ) STACK_SIZE="$2"; shift; shift ;; line, and then issue parse-options -s, you'll trigger the *) pattern's command.

@wilderfield and @Kocjan, MacOS is more FreeBSD (i.e., Unix) than Linux. If you issue man getopt and man getopts (note the plural spelling), you'll see results for both, but the first line of the output will say BSD and will not mention long options. Neither BSD version allows long options like --help or --foobar. For that, you need to install brew install coreutils. For details, see https://stackoverflow.com/a/47542834/1231693. After that, man getopt will NOT say BSD and will mention long options.

For anyone interested in "test driving" what's really happening in this gist, try the following one-liner:

  getopt -o vhns: --long verbose,dry-run,help,stack-size: -n 'parse-options' -- "$@" <<< bash foo --verbose -s 1 bar

If you vary the number and variety of options at the end, you can see how getopt works.

@davidechicco it took me a while to figure this out because get-opt is cryptic, but the colon at the end of stack-size: in the get-opt command means "requires argument". http://www.bahmanm.com/blogs/command-line-options-how-to-parse-in-bash-using-getopt

Thanks for this!!! I hadn't notice and couldn't make my script work.