. You can display the line by line difference between two files with the diff command. diff file1 file2 . The information given by the command tells you what changes need to be made for file1 and file2 to match. If there is no difference between the files you are returned to the shell prompt . diff indicates which lines need be added ( a ), deleted ( d ) or changed ( c ). Lines in file1 are identified with a ( < ) symbol: lines in file2 with a ( > ) symbol. Examples . Did You Know? .