#!/usr/bin/env bash

USAGE="usage: $0 <pid> [-h, -a] [-f, -e] [-s <regexp>]"
OPTIND=2

if [[ ! "$1" =~ ^-?[0-9]+$ ]]; then
	echo $USAGE; exit 1

elif [[ ! -d /proc/$1 ]]; then
	echo "invalid pid '$1'"; exit 1
fi

echo -e "pid '${1}' refers to a running process.\n"

while getopts ":s:hafe" opts; do
	case "${opts}" in
		s)
		  cat /proc/"$1"/status | grep "$OPTARG"
		  ;;
		h) 
		  echo "$USAGE"; DROPBOOL=1
		  ;;
		a)
		  echo "written by ian sutton."; if [[ $DROPBOOL ]]; then exit 0; fi
		  ;;
		f)
		  ls /proc/"$1"
		  ;;
		e)
		  if [[ ! `readlink /proc/$1/exe` ]]; then
			echo "no permissions to read pid '$1's executable path"; exit 1
		  fi

		  echo -n "executable path of pid '$1': "
		  readlink /proc/"$1"/exe
		  ;;
		\?)
		  echo "bad option \"-$OPTARG\""; exit 1
		  ;;
		:)
		  echo $USAGE; exit 1
		  ;;
	esac
	echo -ne "\n"
done

# -h case
#if [[ "$1" -eq "-h" ]]; then
#	echo "$USAGE"; exit 0 
#
# <pid> case
#elif [[ "$1" =~ ^-?[0-9]+$ ]]; then
#	if `ps $1 > /dev/null 2>&1`; then
#		echo "you win!"; exit 0
#
#	else
#		echo -ne "invalid pid\n$USAGE"; exit 1
#	fi
#
# -e <pid> case
#elif [[ "$1" -eq "-e" && "$2" =~ ^-?[0-9]+$ ]]; then
#	if `ps $2 > /dev/null 2>&1`; then
#		echo "you win!"; exit 0;
#
#	else
#		echo -ne "invalid pid\n$USAGE"; exit 1
#
# -s <pid> <regex> case
#elif [[ "$1" -eq "-s" && "$2" =~ ^-?[0-9]+$ ]]; then
#	if `ps $2 > /dev/null 2>&1`; then
#		echo "you win!"; exit 0;
#
#	else
#		echo -ne "invalid pid\n$USAGE"; exit 1
#
#else
#	echo "$USAGE"; exit 1
#fi