diff

Diff command in Linux is used to compare the content of two files line by line and if the difference is found then it will also list differences along with line numbers. Diff command can also be used to compare the contents of two directories.

Syntax :

diff [options] File1 File2 

Special symbols are:

Symbol	Meaning
A	Add
C	Change
D	Delete
'#'	Line numbers
'– – –'	Separates Files in Output
<	File 1
'>'	File 2

Options	Description
–normal	The output displayed is a normal difference (the one that is displayed by default)
-q, –brief	It reports only if the files differ
-s, –report-identical-files	It reports if two files are the same and have no differences between them
-y, –side-by-side	The output is displayed in two-column format
-t, –expand-tabs	It will help in expanding the tabs to spaces in the output format.
-r, –recursive	It will recursively help in comparing any subdirectories that are found
-i, –ignore-case	This option is used in ignoring any case diff in file data.
-a, –text	This option will be treating all the files as text
–help	Prints the options that are available and will exit
-v, –version	output version information and exit

Examples

Lets say we have two files with names a.txt and b.txt containing 5 Indian states.

• $ ls

a.txt  b.txt

• $ cat a.txt

Gujarat
Uttar Pradesh
Kolkata
Bihar
Jammu and Kashmir

• $ cat b.txt

Tamil Nadu
Gujarat
Andhra Pradesh
Bihar
Uttar pradesh

Now, applying diff command without any option we get the following output:

• $ diff a.txt b.txt

0a1
> Tamil Nadu
2,3c3
< Uttar Pradesh
 Andhra Pradesh
5c5
 Uttar pradesh