Head And Tail Commands In Linux Explained With Examples

Head And Tail Commands In Linux Explained With Examples

Getting a portion of text from input files in Linux is a common operation. However, sometimes, we are interested in viewing only a few lines of a file. Linux provides us the head and tail commands to print only the lines in which we are interested in.

Linux head and tail commands are very similar. They are by default, installed in all Linux distributions. Let’s first understand what they are and what they are used for.

In short, as their names imply, the head command prints lines from the beginning of a file, and the tail command prints lines from the end of files. Both commands write the result to standard output.

Now, let’s learn how to use them through examples.

Head command in Linux

The syntax of the head command is pretty straightforward:

head [OPTIONS] FILES

By default, without any option, the head command will display the first 10 lines from the file. Just like this.

head /etc/passwd
root:x:0:0::/root:/bin/bash
bin:x:1:1::/:/usr/bin/nologin
daemon:x:2:2::/:/usr/bin/nologin
mail:x:8:12::/var/spool/mail:/usr/bin/nologin
ftp:x:14:11::/srv/ftp:/usr/bin/nologin
http:x:33:33::/srv/http:/usr/bin/nologin
nobody:x:65534:65534:Nobody:/:/usr/bin/nologin
dbus:x:81:81:System Message Bus:/:/usr/bin/nologin
systemd-journal-remote:x:982:982:systemd Journal Remote:/:/usr/bin/nologin
systemd-network:x:981:981:systemd Network Management:/:/usr/bin/nologin

Of course there are options that we can define while executing the command to get the customized output.

Output a specific number of lines using head command

If you wish to retrieve a different number of lines than the default 10, then -n option is used along with an integer telling the number of lines to be retrieved.

For example, the following command will display the first 3 lines from the /etc/passwd file.

head -n 3 /etc/passwd
root:x:0:0::/root:/bin/bash
bin:x:1:1::/:/usr/bin/nologin
daemon:x:2:2::/:/usr/bin/nologin

Output a specific number of bytes using head command

In addition to, the head command can also print the file content by byte. Just pass the -c option to the command. Keep in mind that newline count as a single character, so if head prints out a newline, it will count it as a byte.

For example, the following command will display the first 8 bytes from the /etc/passwd file.

head -c 8 /etc/passwd
root:x:0

Output multiple files using head command

Of course, the head command can also handle multiple files. For example, the following command will show the first 3 lines of /etc/passwd and /etc/group files.

head -n 3 /etc/passwd /etc/group
==> /etc/passwd <==
root:x:0:0::/root:/bin/bash
bin:x:1:1::/:/usr/bin/nologin
daemon:x:2:2::/:/usr/bin/nologin

==> /etc/group <==
root:x:0:brltty,root
sys:x:3:bin
mem:x:8:

Adding the -q option to the example above will strip headers giving file names.

head -q -n 3 /etc/passwd /etc/group
root:x:0:0::/root:/bin/bash
bin:x:1:1::/:/usr/bin/nologin
daemon:x:2:2::/:/usr/bin/nologin
root:x:0:brltty,root
sys:x:3:bin
mem:x:8:

How to use head command with pipes

The head command can be piped to other commands. In the following example the output of the ls command is piped to head to show the five most recently modified files or folders in /etc directory.

ls -t /etc | head -n 5
ld.so.cache
resolv.conf
systemd
libreoffice
profile.d

By now you should have a good understanding of how to use the Linux head command. Now, let’s take a look at the tail command.

Tail command in Linux

Tail command in Linux is same as the head command. Unlike the head command, however, the tail command prints the last few number of lines (10 lines by default) of a certain file.

The basic syntax of tail command is:

tail [OPTIONS] FILES

For example, the following command will print the last 10 lines from the /etc/locale.gen file.

tail /etc/locale.gen
#zh_HK.UTF-8 UTF-8
#zh_HK BIG5-HKSCS
#zh_SG.UTF-8 UTF-8
#zh_SG.GBK GBK
#zh_SG GB2312
#zh_TW.EUC-TW EUC-TW
#zh_TW.UTF-8 UTF-8
#zh_TW BIG5
#zu_ZA.UTF-8 UTF-8
#zu_ZA ISO-8859-1

Output a specific number of lines using tail command

Similarly to the head command, you can also print the last few lines using the -n option as shown below.

tail -n 3 /etc/locale.gen
#zh_TW BIG5
#zu_ZA.UTF-8 UTF-8
#zu_ZA ISO-8859-1

How to use tail command with pipes

Earlier, we piped the output from head into ls . We can also pipe the output from other commands into tail.

For example, to identify the five files or folders in /etc directory with the oldest modification times, and pipe the output into tail:

ls -t /etc/ | tail -n 5
wpa_supplicant
libpaper.d
papersize
mdadm.conf
gssapi_mech.conf

Watch a file for changes using tail command

There is one more powerfull feature in tail command. Sometimes the input file we want to check is changing. For example, a running application may append its output to a log file. If we execute the tail command with the -f option on the changing file, all newly added lines will be appended to standard out. This might be by far the most useful and commonly used option for tail command.

For example, you can see new lines that are added to the end of a Nginx log file, as they are added, like this:

tail -f /var/log/nginx/access.log
172.16.1.122 - - [08/Apr/2021:08:15:32 +0000] "POST /wp-admin/admin-ajax.php HTTP/1.1" 200 109 "https://linuxwizard.com/wp-admin/post.php?post=18254&action=edit" "Mozilla/5.0 (X11; Linux x86_64; rv:87.0) Gecko/20100101 Firefox/87.0" 
172.16.1.122 - - [08/Apr/2021:08:19:27 +0000] "GET /feed/ HTTP/1.1" 304 0 "-" "Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1" 
172.16.1.122 - - [08/Apr/2021:08:19:49 +0000] "HEAD /feed/ HTTP/1.1" 200 0 "-" "Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/77.0.3865.120 Safari/537.36" 

As each new log entry is added to the log file, tail will update its display in the terminal window.

How to use head and tail commands together in Linux

As tail and head commands print different parts of files, we can combine these two to print some advanced filtering of file content. For example, if you want to read the content from the middle of any file, you have to use the both commands together.

Let’s say we want to get from the 5th to the 10th line from the /etc/passwd file. At first, head command will retrieve first 10 lines and tail command will retrieve the last 5 line from the output of head command.

head -n 10 /etc/passwd | tail -n 5
http:x:33:33::/srv/http:/usr/bin/nologin
nobody:x:65534:65534:Nobody:/:/usr/bin/nologin
dbus:x:81:81:System Message Bus:/:/usr/bin/nologin
systemd-journal-remote:x:982:982:systemd Journal Remote:/:/usr/bin/nologin
systemd-network:x:981:981:systemd Network Management:/:/usr/bin/nologin

Conclusion

That’s all for now. In this article we’ve learned some typical usages of both commands through examples. As you can see, both the tail and the head commands are very useful for controlling exactly what file content will print to the screen. Certainly, they are flexible commands that can improve the management of your files greatly. Give them a try.

Need more details? Check the head and the tail commands man pages.

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