havecmd

#!/usr/bin/env bash
# Often used like:
# havecmd -V 'Install from github.com/...' some_command || exit $?
# To exit in my shell scripts if a required command isn't found
#
# this extends 'command -v' to optionally report errors

set -e

main() {
	local usage missing_command_text report_missing
	# shellcheck disable=SC2016
	usage='havecmd [-v] [-V MISSING_COMMAND_TEXT] COMMAND

Provide [-v] (verbose) to report to the user if the
COMMAND is not found on their $PATH

If the COMMAND is not found, -V MISSING_COMMAND_TEXT can be provided
to provide a custom error to the user (e.g. describe how to install/configure)

To enable verbose through a environment variable:

export HAVECMD_REPORT=1

havecmd awk || exit $?
havecmd evry -V "Install from ..." || exit $?'

	report_missing=0
	missing_command_text=''

	[[ -n "$HAVECMD_REPORT" ]] && report_missing=1

	[[ "$1" == "--help" ]] && {
		printf "%s\n" "$usage"
		exit 10
	}

	while getopts "hV:v" opt; do
		case "$opt" in
		h)
			printf "%s\n" "$usage"
			exit 10
			;;
		v)
			report_missing=1
			;;
		V)
			report_missing=1
			missing_command_text="$OPTARG"
			;;
		?)
			printf 'Unknown flag: %s\n' "$opt"
			printf "\n%s\n" "$usage"
			return 10
			;;
		esac
	done
	shift "$((OPTIND - 1))"
	COMMAND="${1:?Must provide COMMAND to check as argument}"
	if command -v "${COMMAND}" >/dev/null 2>&1; then
		exit 0
	else
		if ((report_missing)); then
			printf "havecmd: Could not find '%s' on your \$PATH." "$COMMAND" >&2
			if [[ -n "$missing_command_text" ]]; then
				echo -e " ${missing_command_text}" >&2
			else
				echo # fix cursor location
			fi
		fi
		exit 2
	fi
}

main "$@" || exit $?