bash_script.sh.template

#!/usr/bin/env bash

###################################################################
# Script Name    : bash_script.sh.template
# Description    : Template for a bash script with options.
# Args           : None
# Author         : Doug Emery
# Email          : hummus.augment_0r@icloud.com
#
# Adapted from a gist by Ariel Balter, https://github.com/abalter:
#
#  https://gist.github.com/abalter/4f1375985b99b84e62fcc0d63ef83174u
#
###################################################################

### utility variables
CMD=$(basename $0)
THIS_DIR="$( cd -- "$(dirname "$0")" >/dev/null 2>&1 ; pwd -P )"
TIMESTAMP=$(date +"%Y-%m-%d")

### preallocate variables
required=
optional_hasarg=
got_opt_arg=false
optional_noarg=false
has_default="DEFAULT"

### initialize (clear) opt parsing variables
OPTIND=
OPTARG=
opt=

function usage {
  echo "Usage: ${CMD} [-h] -a REQ [-b OPTHAS] [-c] [-d OPTDEF]"
}

function description {
  cat <<EOF
Description:
------------
This demonstrates parsing arguments with getopts

Options:
-------------------
-h          Print this help message and exit.
-a REQ      Required opt that takes an argument.
-b OPTHAS   Optional opt that takes an argument.
-c          Optional opt that does not take an argument.
-d OPTDEF   If given, sets value of has_default to OPTDEF.
            Otherwise, the value of has_default defaults to
            DEFAULT.

EOF
}

while getopts "ha:b:cd:" opt; do

    case "$opt" in
        h)
            usage
            description
            exit 0
            ;;
        a)
            required=${OPTARG}
            ;;
        b)
            optional_hasarg=${OPTARG}
            got_opt_arg=true
            ;;
        c)
            optional_noarg=true
            ;;
        d)
            has_default=${OPTARG}
            ;;
        ?)
            usage
            echo "Error: did not recognize option, ${OPTARG}."
            echo "Please try -h for help."
            exit 1
            ;;
    esac
done

if [[ "$required" == "" ]]; then
    echo "ERROR: Required option -a not set."
    echo "Please try -h for help."
    exit 1
fi

echo "required: $required"

if [[ "$got_opt_arg" == true ]]; then
    if [[ "$optional_hasarg" == "" ]]; then
        echo "-b option set but no argument given"
        echo "Please try -h for help."
        exit 1
    else
        echo "optional_hasarg: $optional_hasarg"
    fi
else
    echo "optional_hasarg not set"
fi

if [[ "$optional_noarg" == true ]]; then
    echo "optional_noarg set"
else
    echo "optional_noarg not set"
fi

echo "has_default: $has_default"