Tail Command in Linux with Examples

Understanding the Linux tail command is fundamental for anyone delving into the world of Linux-based systems. This command, known for its efficiency and simplicity, plays a pivotal role in file management and system monitoring. In this guide, we focus on demonstrating how to use the tail command in Linux, offering insights into its practical applications and utility. The tail command is particularly valuable for viewing the most recent parts of a file, making it a go-to tool for system administrators and developers alike.

Here are some key features of the Linux tail command:

• Real-time Monitoring: It allows users to view the most recent updates to a file in real-time, which is essential for monitoring log files and system processes.
• Customizable Output: Users can specify the number of lines to display, tailoring the output to their specific needs.
• Combination with Other Commands: The tail command can be seamlessly integrated with other Linux commands for more complex operations, enhancing its versatility.
• Simplicity and Accessibility: Its straightforward syntax makes it accessible to users of all skill levels.

These attributes make the tail command an indispensable tool in the Linux toolkit. As we delve further into this guide, you’ll learn the nuances of utilizing this command to streamline your work on Linux systems, enhancing both efficiency and effectiveness.

Understanding and Utilizing the Linux Tail Command

The Basics of the Tail Command

The Linux tail command is an essential utility for displaying the end of a file. Typically, it shows the last 10 lines but can be adjusted to show a different number of lines using the -n option. This functionality is crucial for monitoring the latest updates to a file, especially log files, in real-time.

Syntax of the Tail Command

The syntax for the tail command is straightforward:

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

Each part of this syntax plays a specific role. The [OPTION] allows for customization, such as specifying the number of lines to display, and [FILE] indicates the file you are accessing.

Tail Command in Linux: Essential Use Cases

Displaying the Last Lines of a File

The tail command in Linux serves the primary function of showing the end of a file. For instance, executing:

tail example.txt

This will display the last 10 lines of “example.txt”. This command is particularly useful for quickly accessing the most recent entries in log files or any file where the latest information is appended at the end.

Specifying the Number of Lines

To view a specific number of lines, use the -n option. For example:

tail -n 20 example.txt

This command will show the last 20 lines of “example.txt”. Adjusting the number of lines displayed by the tail command can be especially helpful when you need to review a certain portion of recent data that exceeds the default 10 lines.

Viewing Multiple Files Simultaneously

A powerful feature of the tail command is its ability to display the ends of multiple files concurrently. For example:

tail file1.txt file2.txt

This command will display the last 10 lines of both “file1.txt” and “file2.txt”. This capability is extremely beneficial for comparing the latest updates or entries across different files, such as multiple log files in system monitoring.

Advanced Applications of the Linux Tail Command

Continuously Monitoring File Updates

The tail command can be used to monitor file updates in real-time using the -f option. For example:

tail -f example.txt

This command keeps the tail window open, displaying new lines added to “example.txt” as they occur. It’s invaluable for tracking live updates, such as monitoring real-time logs in server management.

Displaying Specific Bytes Instead of Lines

Tail can display the final bytes of a file using the -c option. For instance:

tail -c 100 example.txt

This shows the last 100 bytes of “example.txt”. This is particularly useful when dealing with files where byte-specific information is more relevant than line-based data.

Checking Multiple Files with Headers

When checking multiple files, use tail with the -q option to include headers indicating file names:

tail -q file1.txt file2.txt

You can also combine the head and tail commands to display a specific range of lines in a file. For example, to display lines 11 to 20 of the “example.txt” file, enter the following command:

head -n 20 example.txt | tail -n 10

This command displays the last 10 lines from both files, preceded by their respective filenames. It’s useful for distinguishing content when simultaneously monitoring multiple files.

Displaying Lines Starting from a Specific Point

To display lines starting from a specific line number, use the + sign with -n. For example:

tail -n +15 example.txt

This command displays all lines starting from line 15 of “example.txt”. It’s useful for viewing content from a certain point onward.

Combining Tail with Other Commands

Tail can be combined with other Linux commands for more complex operations. For example:

tail example.txt | grep "error"

This command displays the last 10 lines of “example.txt” and filters them to show only lines containing the word “error”.

Suppressing Error Messages

To suppress error messages, particularly when files may not exist or are inaccessible, use the -s option:

tail -s file1.txt file2.txt

This command will display the last lines of the files without showing error messages for missing or inaccessible files.

Displaying File Changes with Delay

For less frequent updates, use the -s option with -f to add a delay. For example:

tail -f -s 10 example.txt

This command updates the display every 10 seconds, showing the latest additions to “example.txt”. It is suitable for monitoring files where updates are not continuous but occur at regular intervals.

Tail Command: More Examples

The tail command in Linux can display the contents of multiple files at once. This can be useful when you have related information stored in separate files and want to display the information together.

For example, let’s consider two files named “states.txt” and “capitals.txt” that contain the names of American states and their capitals, respectively.

The “states.txt” file might look something like this:

Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
Florida
Georgia

And the “capitals.txt” file might look something like this:

Montgomery
Juneau
Phoenix
Little Rock
Sacramento
Denver
Hartford
Dover
Tallahassee
Atlanta

To display the names of American states and their capitals together, we can use the tail command to display the contents of both files. To do this, enter the following command:

paste states.txt capitals.txt | tail

Example Output:

Georgia
Atlanta

As you can see, the tail command displays the contents of both files, and the “paste” command combines the contents of the two files into a single output. The result is a display of the names of American states and their capitals, with each state and capital appearing on the same line.

Advanced Options of the Tail Command in Linux with American State and Capital Examples

In addition to displaying the last few lines of a file, the tail command in Linux offers several advanced options that can be used to customize the output. Let’s consider two files named “states.txt” and “capitals.txt” that contain the names of American states and their capitals, respectively.

tail -n 3 states.txt

Example output:

West Virginia
Wisconsin
Wyoming

You can also use the “-n” option without the “n” character as long as you use the “-” symbol. For example:

tail -3 states.txt

The tail command also has an option “+,” which is not present in the head command. With this option, the tail command prints the data starting from a specified line number in the file instead of from the end of the file. For the command “tail +n file_name,” the data will start printing from line number “n” until the specified file’s end.

tail +25 states.txt

Example Output:

Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
Washington
West Virginia
Wisconsin
Wyoming

Displaying a Specific Number of Bytes

The “-c” option can display a specific number of bytes from the end of a file. For example, if you want to display the last 6 bytes of the “states.txt” file, enter the following command:

tail -c -6 states.txt

Example output:

oming

Alternatively, if you want to display all the data after skipping 263 bytes from the start of the “states.txt” file, enter the following command:

tail -c +263 states.txt

Suppressing File Names

When displaying the contents of multiple files, the tail command will display the name of each file before the contents of that file. To suppress the file names, use the “-q” option. For example, enter the following command to display the contents of both the “states.txt” and “capitals.txt” files without file names:

tail -q states.txt capitals.txt

Example Output:

West Virginia
Wisconsin
Wyoming
Charleston
Cheyenne

Displaying File Names

If you want to display the name of each file before its contents, use the “-v” option. For example, enter the following command to display the name of the “states.txt” file before its contents:

tail -v states.txt

Example output:

==> states.txt <==
West Virginia
Wisconsin
Wyoming

Showing the Version of Tail

To display the version of the tail command currently running on your system, use the “–version” option. For example, enter the following command:

tail --version

Example output:

tail (GNU coreutils) 9.1
Copyright (C) 2022 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Written by Paul Rubin, David MacKenzie, Ian Lance Taylor,
and Jim Meyering.

Monitoring Log Files

System administrators commonly use the “-f” option to monitor log files written by Unix programs as they are running. This option displays the last ten lines of a file and will update as new lines are added. For example, if you have a log file named “logfile,” enter the following command to monitor it:

tail -f logfile

Using Tail with Pipes

The tail command can be combined with other Unix commands using pipes. For example, you can pipe the output of the tail command into the sort command to sort the last 7 state names from the “states.txt” file in reverse order:

tail -n 7 states.txt | sort -r

Example Output:

Wyoming
Wisconsin
West Virginia
Washington
Virginia
Vermont
Utah

You can also use multiple filters for additional processing. For example, you can use the cat, head, and tail commands to store the output in a file named “list.txt.”

cat states.txt | head -n 20 | tail -n 5 > list.txt

The above command first uses the cat command to display the contents of the “states.txt” file, then pipes the output to the head command, which displays the first 20 lines. The output from the head command is then piped to the tail command, which displays the last 5 lines, and finally, the output is stored in the file “list.txt” using the directive operator.

Conclusion

The tail command in Linux is a simple yet powerful tool that allows you to display the last few lines of a file. Whether you’re a system administrator or a developer, the tail command is essential in your toolkit. By following this guide, you should now understand how to use the tail command in Linux, as well as some of the advanced features and options it offers.