How to Use the Tail Command

In this guide, you’ll learn how to use the tail command. Using tail is a simple way to show the ends of files, for example, when analyzing logs and other text files that change over time. It may also be combined with other tools for selective, real-time monitoring. When performing administrative tasks on your Linode, tail is one of the most useful tools available.

1. Enter the tail command, followed by the file you’d like to view:

   tail /var/log/auth.log
   

   This will print the last ten lines of the /var/log/auth.log file to your terminal output.

2. To change the number of lines displayed, use the -n option:

   tail -n 50 /var/log/auth.log
   

   In this example, the last 50 lines will be shown, but you can modify this number to show as many or as few lines as you need.

3. To show a real-time, streaming output of a changing file, use the -f or --follow options:

   tail -f /var/log/auth.log
   

   This will print the end of the file to your screen, and update it as the file changes. For example, you can use this option with /var/log/auth.log (on Debian and Ubuntu systems) to show your access log in real time. This will run as a foreground process, so to cancel it, press CTRL+C.

4. Tail can even be combined with other tools like grep to filter the results:

   tail /var/log/auth.log | grep 198.51.100.1
   

   This command would search the last ten lines of your access log and only display those that contain the IP address 198.51.100.1. You can also apply options to tail in order to show more or less lines, view the filtered results in real time, and more.

These are just the basics of how to use tail. It is an incredibly useful tool with many more options than we’ve listed here. To learn more advanced techniques, please check out our full guide on the tail command.