How to Use Tail Command in Linux

How to Use Tail Command in Linux
How to Use Tail Command in Linux

Use Tail Command in Linux

Tail command prints last N number of lines from the given file. Tail command is complimentary of head command. This command mostly used to monitor log files which are changing continuously in real time. Tails command by default prints last 10 lines if number of lines is not specified explicitly. In this tutorial you are going to learn how to use tail command in Linux.

Prerequisites

Before you start to install Yarn on Ubuntu 18.04. You must have the non-root user account on your system with sudo privileges.

Basic Syntax

Following is the basic syntax for tail command.

tail [OPTION]... [FILE]...

OPTION : You can check the list of options available for tail command visiting this link.
FILE : Here you can use one sr multiple files.

Using Tail Command

Following command will print last 10 lines of newfile.txt file. When no option specifies for number of lines it will by default prints 10 lines.

tail newfile.text

How to Print Specific Number of Lines

Following is the basic syntax to print specific number of lines from the give file. In following command -n option is used to specify number of lines.

tail -n  newfile.txt

To print last 20 lines of newfile.txt you should use following command.

tail -n 20 newfile.txt

How to Display Multiple Files

If you want to display last 10 lines of multiple files then use following command. This command will print last 10 lines of newfile1.txt and newfile2.txt.

tail newfile1.txt newfile2.txt

To print, last 20 lines of multiple files use the following command.

tail -n 10 newfile1.txt newfile2.txt

Both above commands will print the last lines with their filenames also. If you want filename should not be printed the use -q option with tail command.

tail -q newfile1.txt newfile2.txt

How to Watch a File For Changes

To Watch File changes in realtime use -f option.

tail -f newfile.txt

Now press CTRL+c to exit.

You can use -f (–follow) for monitoring log files in Linux. To check access.log file use following command:

tail -f /var/log/nginx/access.log

Now press CTRL+c to exit.

If you want to monitor file when its recreated use tail command with -F option:

tail -F /var/log/nginx/access.log

How to Display Specific Number of Bytes

If you want to display specific number of Bytes -c option is used called as –bytes with tail command.

To display last 100 bytes from the file newfile1.txt use following command:

tail -c 100 filename.txt

To display last 1 kilobytes (1024 bytes) from the file newfile1.txt run below command:

tail -c 1K filename.txt

In above command k used to multiply with 1024. You can use b to multiply with 512, KB to multiply with 1000, MB to multiply with 1000000 while m to multiply with 1048576.

How to Use Tail Command With Another Commands

You can pipe tail command with another commands. By using tail command with other commands you can do useful operations as given below.

Following command is used to print last 100 bytes from newfile.txt to output.txt file:

cat newfile.txt | tail -c 100  > output.txt

Use following command to print last 10 lines of file newfile.txt sorted in reverse order:

tail -n 10 newfile.txt | sort -r

Conclusion

You have successfully learned how to use tail command in Linux. If you have any queries regarding this then please don’t forget to comment below.