Linux Shell Scripting Cookbook - Third Edition

How to do it...

The diff utility reports the differences between two files.

1. To demonstrate diff behavior, create the following files:

File 1: version1.txt

         this is the original text 
         line2 
         line3 
         line4 
         happy hacking ! 

File 2: version2.txt

       this is the original text  
       line2 
       line4 
       happy hacking !  
       GNU is not UNIX 

2. Nonunified diff output (without the -u flag) is:

        $ diff version1.txt version2.txt 
        3d2
        <line3
        6c5
        > GNU is not UNIX

3. The unified diff output is:

        $ diff -u version1.txt version2.txt
        --- version1.txt  2010-06-27 10:26:54.384884455 +0530 
        +++ version2.txt  2010-06-27 10:27:28.782140889 +0530 
        @@ -1,5 +1,5 @@ 
        this is the original text 
        line2
        -line3
        line4    
        happy hacking ! 
        -
        +GNU is not UNIX

 The -u option produces a ...