Parse bash command options with getopt(1)

options-avanced.sh

#!/usr/bin/env bash

# “a” and “arga” have optional arguments with default values.
# “b” and “argb” have no arguments, acting as sort of a flag.
# “c” and “argc” have required arguments.

# getopt bin
getopt=/usr/local/opt/gnu-getopt/bin/getopt

# set an initial value for the flag
ARG_B=0

# read the options
TEMP=$($getopt -o a::bc: --long arga::,argb,argc: -n 'test.sh' -- "$@")
eval set -- "$TEMP"

# extract options and their arguments into variables.
while true ; do
    case "$1" in
        -a|--arga)
            case "$2" in
                "") ARG_A='some default value' ; shift 2 ;;
                *) ARG_A=$2 ; shift 2 ;;
            esac ;;
        -b|--argb) ARG_B=1 ; shift ;;
        -c|--argc)
            case "$2" in
                "") shift 2 ;;
                *) ARG_C=$2 ; shift 2 ;;
            esac ;;
        --) shift ; break ;;
        *) echo "Internal error!" ; exit 1 ;;
    esac
done

# do something with the variables -- in this case the lamest possible one :-)
echo "ARG_A = $ARG_A"
echo "ARG_B = $ARG_B"
echo "ARG_C = $ARG_C"

options.sh

#!/usr/bin/env bash

# getopt bin
getopt=/usr/local/opt/gnu-getopt/bin/getopt

args=$($getopt --options=d --long=delete -- "$@")

eval set -- "$args"

delete=false

while true ; do
    case "$1" in
        -d|--delete)
          delete=true
          shift
          ;;
        --)
          shift
          break
          ;;
        *)
          echo "Error"
          exit 1
          ;;
    esac
done

if $delete
then
  echo 'Delete is ON'
else
  echo 'Delete is OFF'
fi