The diff command

The diff command is used to find differences between two files. Let's see a few examples to find out its usage. The content of file1 is as follows:

I go for shopping on Saturday 
I rest completely on Sunday 
I use Facebook & Twitter for social networking 

The content of file2 is as follows:

Today is Monday. 
I go for shopping on Saturday 
I rest completely on Sunday 
I use Facebook & Twitter for social networking 

Type the diff command:

    $ diff file1 file2

The output will be this:

    0a1
    > Today is Monday

In the output, 0a1 tells us that line number 1 is added in file2. Let's see another example with line deletion. The content of file1 is as follows:

Today is Monday 
I go for shopping on Saturday 
I rest completely on Sunday 
I use Facebook & Twitter for social networking 

The content of file2 is as follows:

Today is Monday 
I go for shopping on Saturday 
I rest completely on Sunday 

Type the diff command:

    $ diff file1 file2

The output is as follows:

    4d3
    < I use Facebook & Tweeter for social networking.

In the output, 4d3 tells us that line number 4 is deleted in file2. Similarly, the c command will show us changes to a file as well.