#!/bin/bash
#
# backup-arg.sh - make copy for specified files 
#
# usage: ./backup-args.sh [filename] ...
# 
# input: list of file names
# output: 
#
# CS50, Spring 2022

ret=0

for i in "$@"
do
  # check if a given file exists
  if [ ! -f "$i" ]
  then
    echo 1>&2 "file $i does not exist"
    ((ret+=1))
    continue
  fi

  if [ -f "$i.bak" ]
    then
      diff "$i" "$i.bak"
    else
      echo "creating backup for $i..."
      cp "$i" "$i.bak"
  fi
done

exit $ret