#!/bin/bash

get_ident() {
	local pid=$1
	ps h -o lstart -p "$pid"
}

is_running() {
	local pidfile=$1
	if [[ -f "$pidfile" ]]; then
		cat "$pidfile" | while read pid ident1; do
			ident2="$(get_ident "$pid")"
			if [[ "$ident1" = "$ident2" ]] && [[ -n "$ident2" ]]; then
				return 0
			else
				return 1
			fi
		done
	else
		return 1;
	fi
}

main() {
	# Parse arguments
	if [[ $1 = '-i' ]]; then
		shift
		id=$1
		shift
	else
		id=$1
	fi

	# Init variables
	TMP=${TMPDIR-/tmp}/daemon
	PIDFILE="$TMP/$id.pid"
	OUTFILE="$TMP/$id.out"
	ERRFILE="$TMP/$id.err"

	# Run
	if is_running "$PIDFILE"; then
		echo "daemon: \`$id' is already running"
	else
		mkdir -p "$TMP"
		echo "daemon: starting \`$id'"
		nohup "$@" > "$OUTFILE" 2> "$ERRFILE" &
		pid=$!
		echo "$pid" "`get_ident $pid`" > "$PIDFILE"
	fi
}

main "$@"