The tail command in Linux displays the last part of a file or stream. It’s a powerful tool for viewing the end of a file without loading the entire file. “Tail” refers to the “tail end” or the last part.

Commonly used to monitor log files in real-time, displaying new lines added to the end. Useful for quickly checking the last few lines or extracting specific lines from the end.

Available on Unix-like systems like Linux, macOS, and BSD. It’s a standard utility in the GNU Core Utilities package, pre-installed on most Linux distributions.

Official page: https://www.gnu.org/software/coreutils/manual/html_node/tail-invocation.html

Written in C for efficiency and system access, making it fast and lightweight for handling large files and streams.

Installation on Supported Operating Systems

Usually pre-installed. Check with:

tail --version

If not found or needing installation, use your distribution’s package manager.

Ubuntu/Debian:

sudo apt-get install coreutils

CentOS/Fedora:

sudo yum install coreutils

Arch Linux:

sudo pacman -S coreutils

After installation, tail should be available.

Usage and Examples

Basic syntax:

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

Common options and examples:

Display the last 10 lines of a file:

tail file.txt

Displays the last 10 lines of “file.txt”. Displays all lines if the file has fewer than 10.

Display a specific number of lines:

tail -n 5 file.txt

Displays the last 5 lines of “file.txt”. Change the number for a different amount.

Display lines in real-time:

tail -f file.txt

Displays the last 10 lines of “file.txt” and updates as new lines are added. Monitors log files in real-time.

Display lines in reverse order:

tail -r file.txt

Displays the last 10 lines of “file.txt” in reverse order. Useful for viewing the oldest lines.

Similar Commands and Benefits

Other similar commands:

head:

The counterpart to tail, displaying the *first* part of a file or stream. Extracts the beginning of a file for preview.

less:

A pager utility for scrollable viewing of file contents. Similar to tail for displaying the end, but with searching and navigation features.

grep:

Searches for specific patterns or lines. Can be combined with tail to extract lines from the end matching a specific pattern.

tail suits system administrators, developers, and analysts for monitoring logs, tracking changes, and extracting information from large files.

Scripts Examples

Three script examples using tail:

Script 1: Monitor Apache Access Logs

#!/bin/bash

tail -f /var/log/apache2/access.log | grep "404"

Monitors the Apache access log file and filters lines containing “404” for tracking 404 errors in real-time.

Script 2: Check Disk Space Usage

#!/bin/bash

tail -n 5 /var/log/syslog | grep "disk space"

Displays the last 5 lines of the system log and filters lines containing “disk space” to check for warnings or errors.

Script 3: Monitor Application Logs

#!/bin/bash

tail -f /var/log/application.log | awk '/ERROR/ { print $0 }'

Monitors the application log and prints out lines containing “ERROR” for tracking errors in real-time.

List of Possible Functions and Constants

Function/Constant	Description
-n, --lines=K	Display the last K lines of the file
-f, --follow	Output appended data as the file grows
-r, --reverse	Display lines in reverse order
--help	Display help information
--version	Display version information

Conclusion

tail is a powerful tool for viewing the end of files or streams in Linux. Widely used for log monitoring, change tracking, and information extraction, it’s a fast, efficient, and essential tool.

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