named arguments sample for bash

named-arguments.sh

#!/bin/bash

#set -e

help() {
    cat <<EOF
A minimalistic script to showcase named arguments in bash.

The following flags are required.
       --req-arg        If required arg is not specified execution is interrupted.

The following flags are optional.
       --opt-arg        Variable defaults to 'default'
EOF
    exit 1
}

while [[ $# -gt 0 ]]; do
    case ${1} in
        --req-arg)
            REQUIRED_ARG="$2"
            shift
            ;;
        --opt-arg)
            OPTIONAL_ARG="$2"
            shift
            ;;
        *)
            help
            ;;
    esac
    shift
done

# Exiting if required argument is not defined
[ -z "${REQUIRED_ARG}" ] && echo "--req-arg is required, type --help for help" && exit 1;

# Defaulting the optional argument
[ -z "${OPTIONAL_ARG}" ] && OPTIONAL_ARG=default

echo "--req-arg=$REQUIRED_ARG"
echo "--opt-arg=$OPTIONAL_ARG"

Applying named arguments

$ ./named-arguments.sh --req-arg very-important --opt-arg not-so-important
--req-arg=very-important
--opt-arg=not-so-important

Optional argument defaulting to the default value

$ ./named-arguments.sh --req-arg very-important
--req-arg=very-important
--opt-arg=default

Missing Required argument

$ ./named-arguments.sh --opt-arg not-so-important       
--req-arg is required, type --help for help

Help

$ ./named-arguments.sh --help
A minimalistic script to showcase named arguments in bash.

The following flags are required.
       --req-arg        If required arg is not specified execution is interrupted.

The following flags are optional.
       --opt-arg        Variable defaults to 'default'