getopts.sh

#!/usr/bin/env bash

# Example of supporting long (--long) and short (-s) options in bash via getopts

# Shorg options are declared at the beginning of the while block,
# while their counterparts (long options) are declared in the case block

# If the option requires a value, it should be declared as r: (letter followd by colon)
# and validated with needs_arg() when parsing.
# Alternatively die "Error message" is used to stop when we get an option which has not been declared

# Source: https://stackoverflow.com/a/28466267/319150

# Example usage:
# ./getopt.sh -f -b bravo
# ./getopt.sh --alpha ABC
# ./getopt.sh --charlie="menu1" --bravo="bravissimo" -a first
# ./getopt.sh -c "the value for 'charlie' option" -f

die() { echo "$*" >&2; exit 2; }  # complain to STDERR and exit with error
needs_arg() { if [ -z "$OPTARG" ]; then die "No arg for --$OPT option"; fi; }

while getopts afb:c:-: OPT; do
  # support long options: https://stackoverflow.com/a/28466267/519360
  if [ "$OPT" = "-" ]; then   # long option: reformulate OPT and OPTARG
    OPT="${OPTARG%%=*}"       # extract long option name
    OPTARG="${OPTARG#$OPT}"   # extract long option argument (may be empty)
    OPTARG="${OPTARG#=}"      # if long option argument, remove assigning `=`
  fi
  case "$OPT" in
    f         )    filter=true ;;
    a | alpha )    alpha=true ;;
    b | bravo )    needs_arg; bravo="$OPTARG" ;;
    c | charlie )  needs_arg; charlie="$OPTARG" ;;
    ??* )          die "No such option --$OPT. See $0 --help for details." ;;  # bad long option
    ? )            exit 2 ;;  # bad short option (error reported via getopts)
  esac
done
shift $((OPTIND-1)) # remove parsed options and args from $@ list

printf "Your input: filter=%s\talpha=%s\tbravo=%s\tcharlie=%s\n" "$filter" "$alpha" "$bravo" "$charlie"