Rewrite of 'Generic Bash Script Options' posted to reddit

generic_bash_script_options.sh

#!/usr/bin/env bash
#
# Generic Bash Script Args

show_help() {
    cat << EOF
Generic Bash Script Args

USAGE: ${0##*/} [OPTIONS] -c PATH -r TIME -n NUM -s NUM
       ${0##*/} [OPTIONS] --copy-from PATH --creation TIME --var-num NUM --step NUM

OPTIONS:
    -h, --help              Show this help message
	
REQUIRED:
    -c, --copy-from PATH    Copy from PATH
    -r, --creation TIME     Creation TIME
    -n, --var-num NUM       Variable NUM
    -s, --step NUM          Step NUM
EOF
}

is_shell_compatible() {
	# Cannot assume bashisms are available
	[ -n "$BASH_VERSION" ] && return 0
	printf '%s\n' "${0##*/} requires the BASH shell" >&2
	return 1
}

is_bash_compatible() {
	(( BASH_VERINFO[0] > 3 )) && return 0
	printf '%s\n' "${0##*/} requires Bash v4.x or newer: '${BASH_VERSION}'" >&2
	return 1
}

require() {
	command -v "${1}" &>/dev/null && return
	printf '%s\n' "Missing dependency: '${1}'" >&2
	return 1
}

has_dependencies() {
	local err i
	
	for i in "grep" "git" "awk" "vim" "rm"; do
		require "${i}" || err="1"
	done
	
	return "${err:-0}"
}

are_required_vars_defined() {
	local i err
	
	for i in "${!requires[@]}"; do
		[[ -n "${requires[$i]}" ]] && continue
		printf '%s\n' "Required option not specified: '${i}'" >&2
		err="1"
	done
	
	if [[ -n "${err}" ]]; then
		show_help
		return 1
	fi
	
	return 0
}

main() {
	local -A required
    local opts
    opts="$(getopt \
        --options hc:r:n:s: \
        --longoptions help,copy-from:,creation:,var-num:,step: \
        --name "${0##*/}" \
        -- "${@}" \
    )"
	
	required=(
		['copy-from']=""
		['creation']=""
		['var-num']=""
		['step']=""
	)

    eval set -- "${opts}"
    while true; do
        case "${1}" in
            -h | --help )       show_help; return 0;;
			-c | --copy-from ) 	required['copy-from']="${2}"; shift;;
			-r | --creation ) 	required['creation']="${2}"; shift;;
			-n | --var-num ) 	required['var-num']="${2}"; shift;;
			-s | --step ) 		required['step']="${2}"; shift;;
            -- )                shift; break;;
            * )                 break;;
        esac
        shift
    done
	
	has_dependencies || return 1
	are_required_vars_defined || return 1
	
	cat <<- EOF
		Copy-From = "${required['copy-from']}"
		Creation  = "${required['creation']}"
		Var-Num   = "${required['var-num']}"
		Step      = "${required['step']}"
	EOF
	return 0
}

( is_shell_compatible && is_bash_compatible ) || exit 2

main "${@}"

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