Linux tail Command: How to Display and Track the Last Part of a File

Linux tail Command: How to Display and Track the Last Part of a File

The tail command in Linux is a powerful utility that allows users to display the last part (or “tail”) of a file. It’s especially useful for monitoring log files or examining large files where only the most recent data is of interest.

In this article, we’ll explore some of the most common and practical ways to use the tail command, with tips to make the most of its features.

---

Basic Usage of the tail Command

By default, the tail command shows the last 10 lines of a file. To customize how many lines are displayed, you can use the -n option.

For example, to display the last 55 lines of the file /var/log/messages, you can use the following command:

$ tail -n 55 /var/log/messages

---

Monitoring File Changes in Real Time

One of the most powerful features of tail is the ability to track file updates in real time using the -f option. This is particularly useful when monitoring log files for changes.

For example:

$ tail -n 55 -f /var/log/messages

This command shows the last 55 lines of the file /var/log/messages and keeps the terminal open, displaying any new lines added to the file as they appear. This is invaluable when debugging or keeping an eye on system events.

---

Combining tail with Other Utilities

The tail command becomes even more versatile when combined with other Linux tools. Here are some common use cases:

1. Viewing Long Outputs with more

If you need to view a large number of lines and prefer scrolling through them interactively, you can pipe the output of tail to the more command:

$ tail -n 255 -f /var/log/messages | more

This command displays the last 255 lines of /var/log/messages and allows you to navigate through the output page by page.

2. Filtering Output with grep

To focus on specific information in a file, you can combine tail with grep to filter lines based on keywords. For instance, if you’re interested in logs related to the named service, use the following:

$ tail -n 55 -f /var/log/messages | grep "named"

This will display and track only the lines containing the word “named” from the last 55 lines of the log file, along with any new matching entries that appear.

---

Practical Tips for Using tail

1. Debugging Made Easy: Use tail -f to monitor live logs during software deployments or server debugging.
2. Optimizing System Monitoring: Combine tail with utilities like grep or awk to isolate and analyze critical log data.
3. Check Permissions: Ensure you have the necessary read permissions for the file you’re trying to access with tail.

---

Conclusion

The tail command is an essential tool for Linux users, providing an efficient way to access the most recent data in a file, monitor changes in real time, and filter information for specific use cases. Whether you’re debugging an issue, analyzing logs, or just exploring system behavior, mastering tail and its options can significantly enhance your productivity.

Do you use tail in your daily work? Let us know your favorite tips or tricks in the comments below!