#!/usr/bin/env bash

## Run a command as a background process or kill all instances of the command if
## any are running.
##
## Usage: toggle <command> [<command_arg>...]
##
## Dependencies: GNU coreutils, GNU sed, procps
##
## I use this script to play/stop my favorite white noise MP3
## <https://boxfansound.com/> via a window manager key binding.

set -euo pipefail
shopt -s inherit_errexit

die() { echo -e "$(basename "$0"): $1" >&2; exit 1; }

[[ " $* " =~ ' --help ' ]] && sed -n 's/^## *//p' "$0" && exit
(( $# >= 1 )) || die 'missing argument'

cmd=$1; type "$cmd" &> /dev/null || die "command not found: $cmd"
cmd_args=("${@:2}")

pkill "${cmd::15}" || ($cmd "${cmd_args[@]}" &> /dev/null &)