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tail is a command-line utility that allows you to display the last part of files. It is a highly versatile tool, commonly used in system administration and cybersecurity to monitor log files, trace errors, and observe real-time system activities. This utility is available by default on most Unix-based operating systems, such as Linux and macOS.


The basic syntax for the tail command is:

tail [options] [file_name]
  • options: Flags that modify the behavior of the command.
  • file_name: The name of the file you want to display.

Some common options in tail include:

  • -n [lines]: Output the last [lines] lines, instead of the default last 10 lines.
  • -f: Follow the file as it grows, displaying new content in real time.
  • -F: Similar to -f, but also tries to keep the file open if it’s removed, can’t be accessed or replaced
  • -q: Quiet mode - never output headers with file names
  • -s [seconds]: Sleep for approximately [seconds] between iterations. This is applicable with -f flag.


  • Display the last 10 lines of a file:
tail file_name
  • Display the last 50 lines of a file:
tail -n 50 file_name
  • Monitor a log file in real time:
tail -f log_file
  • Monitor multiple log files in real time:
tail -f log_file1 log_file2 log_file3

Use Cases in Cyber Security

tail is often used by cybersecurity professionals to analyze log files, trace errors, and monitor system activities. Some common use cases include:

  • Identifying unauthorized access attempts by monitoring the contents of the /var/log/auth.log file in real time:
tail -f /var/log/auth.log
  • Analyzing the most recent entries in a web server log file to identify unusual requests or suspicious activities:
tail -n 50 /var/log/apache2/access.log
  • Monitoring system log files to quickly identify and respond to security incidents or anomalies:
tail -f /var/log/syslog

In summary, tail is a powerful and versatile command-line utility that proves to be an invaluable resource for system administrators and cybersecurity professionals, providing real-time monitoring and analysis of log files and system activities.

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