PS: [rocketmouse at archlinux tmp]$ diff file_a.txt file_b.txt 2c2 < 1234 --- > 5678 [rocketmouse at archlinux tmp]$ echo $? 1 The OP might want to google why 'echo $?' returns 1 and what it is good for ;). IMO those are the things a novice should do before maintaining a mail server or port.