grep command is used to search files. The basic syntax is:

grep 'word' file
grep 'word1 word2' file1 file2
grep [option] 'word1 word2' file1 file2

The -n or --line-number grep option

You can pass either -n or --line-number option to the grep command to prefix each line of output with the line number within its input file. The syntax is:

grep -n 'patten' file
grep -n 'patten' file1 file2
grep -n [options] 'pattens' file

In this example search for a patter/word called ‘/dev’ in /etc/fstab file and display line number while displaying the output on screen:

grep -n '/dev' /etc/fstab

Sample outputs:

6:# Accessible filesystems, by reference, are maintained under '/dev/disk'
13:tmpfs                   /dev/shm                tmpfs   defaults        0 0
14:devpts                  /dev/pts                devpts  gid=5,mode=620  0 0

For better result I suggest you pass the –color option to gnu/grep command:

grep -n --color '/dev' /etc/fstab

Sample outputs:

Suggested readings

• For further information and examples see “Linux / UNIX grep Command Tutorial series” or read grep(1) command man page.