Linux - head & tail

Linux head and tail commands practical examples and explanation

Similar to cat command, Head and tail commands deal with displaying the content of a file. But they don’t display the entire content of it, instead show a certain number of lines of the file from head & tail part.

In this section, we will see some of the examples for head command and tail command individually.

Let’s start with head command,

Syntax:

head filename
head -n12 file-name

By default, the head command will show top 10 lines of a file.

Example-1:

Show top lines of a file:

We have a file abclearn_lab4 and to look at its top 10 lines.

[rreddy@abclearn abclearn_dir1]$ head abclearn_lab4.txt
this line should replace the existing one
this is the first line in new file
Hi
this information saves in a new file
Hey, this goes into a file
This is another test line
Testing
Success one
0121313121
New line content

To see top 4 lines of a file,

[rreddy@abclearn abclearn_dir1]$ head -n 4 abclearn_lab4.txt
this line should replace the existing one
this is the first line in new file
Hi
this information saves in a new file

Between -n and 4 you can keep the space or remove it. It works in both ways.

head -n4 abclearn_lab4.txt

Practical usage:

The tail command will show the number of lines from the bottom of the file.

Syntax:

tail filename
tail -n number-of-lines file-name

Example-1:

Show bottom lines of a file:

Similar to head command it shows bottom 10 lines of a file by default.

[rreddy@abclearn abclearn_dir1]$ tail abclearn_lab4.txt
How are you
closing this file here
Test line
Test line
Test line
Test line
Test line
Test line
Test line

If we want to see only last 3 lines of a file abclearn_lab4.txt

[rreddy@abclearn abclearn_dir1]$ tail -n 3 abclearn_lab4.txt
How are you

closing this file here.

Note: 

head and tail commands will display even empty lines as part of the output.

Exampe-2:

To see continuous updates of a file:

The tail command has a wonderful feature to show, continuous updates of a file to the bottom of the page.

We can use “-f” option with tail command,

Syntax:

tail -f file-name

[rreddy@abclearn abclearn_dir1]$ tail -f errorfile

Practical usage:

Assume we have a log file and want to observe the content updated dynamically.

Let’s take a file, which is having some 90 lines in it. And I want to display lines from line number 20 to 35. How can we do it?

We can use the combination of head and tail commands to display the output.

[rreddy@abclearn abclearn_dir1]$ head -n35 filename | tail -n15