How to use head command

Introduction

Head : is built in command on unix systems or unix-like operating systems Like :

• 386BSD.
• Arch Linux.
• AIX.
• Android.
• BSD NET/2.
• Debian.
• DragonFly BSD.
• GNU Hurd.

Usage : used to display the top lines or bytes of the text files or the beginning of piped data.

How to use it ?

• You can use it to display the beginning of large text file Like : systems log .

• It can read top 10 lines by default :

head /var/log/user.log

• Or you can specify the number of lines that you need to display it.

head -n 2  /var/log/user.log

head --lines=2  /var/log/user.log

Hint : –lines= number of lines === -n number of lines

OUTPUT:

root@unixcop:~# head --lines=2  /var/log/user.log
Sep 28 15:59:47 unixcop vmnet-natd: RTM_NEWLINK: name:eth0 index:2 flags:0x00001003
Sep 28 15:59:47 unixcop vmnet-natd: RTM_NEWLINK: name:wlan0 index:3 flags:0x00011043
root@unixcop:~# 

• You can either display bytes from text file
• bytes mean one character .. i will create text file with 10 char

echo "CharNum8--" > ~/bytes.txt

• Then i will display the first 8 char using head

head -c 8 ~/bytes.txt

head --bytes=8 ~/bytes.txt

OUTPUT:

CharNum8

• You can use head to read from many different files
• I can use this option for comparison.

head -q unix.txt cop.txt 

head --quiet  unix.txt cop.txt

• I can use head with option verbose to display the content of files with name of the file above

head -v unix.txt 

head --verbose unix.txt 

OUTPUT:

==> unix.txt <==
Name         Email 
Mostafa      [email protected]

I will merge between verbose option and quiet option to clarify the usage of them

OUTPUT:

root@unixcop:~# head --quiet --verbose unix.txt cop.txt 
==> unix.txt <==
Name         Email 
Mostafa      [email protected]

==> cop.txt <==
Name         Email 
Mostafa      [email protected]
root@unixcop:~# 

• I can use it with pipeline

cat /var/log/user.log | head -n 3

ls -lah /root | head -n 5

• Here I can use head to store the result of command in text file

cat /var/log/user.log | head -n 3 > output.txt

OUTPUT:

root@unixcop:~# cat /var/log/user.log | head -n 3 > output.txt
root@unixcop:~# cat output.txt 
Sep 28 15:59:47 unixcop vmnet-natd: RTM_NEWLINK: name:eth0 index:2 flags:0x00001003
Sep 28 15:59:47 unixcop vmnet-natd: RTM_NEWLINK: name:wlan0 index:3 flags:0x00011043
Sep 28 15:59:47 unixcop vmnet-natd: RTM_NEWROUTE: index:3
root@unixcop:~# 

• You can know the head version by typing :

head --version 

• For more help you can use this option:

head --help 

Conclusion:

This article clarify how to use head command with practical examples.