The tail command in Linux displays the end of a text file or input stream, making it ideal for monitoring logs, checking recent data, or tracking real-time updates. By default, it shows the last 10 lines of a file, but you can adjust the number of lines or bytes. Its -f (follow) mode is particularly useful for live log monitoring. Below are practical examples to master tail:
Contents
Display the Last 10 Lines of a FileShow a Specific Number of LinesMonitor Real-Time Updates in a LogTrack Logs Even After File RotationDisplay Bytes Instead of LinesView the End of Multiple FilesSuppress Filename HeadersPipe Output from Another CommandSave the Last Few Lines to a FileCombine with head to Extract Middle Sections
Display the Last 10 Lines of a File
tail file.txt
Shows the default last 10 lines of file.txt.
Show a Specific Number of Lines
tail -n 20 file.txt
Displays the last 20 lines of the file.
Monitor Real-Time Updates in a Log
tail -f /var/log/syslog-f(follow) keeps the output open and appends new lines in real time.- Press
Ctrl+Cto exit.
Track Logs Even After File Rotation
tail -F /var/log/nginx/access.log-F(capital F) follows the file even if it’s recreated (e.g., log rotation).
Display Bytes Instead of Lines
# Display last 20 bytes of a file
tail -c 20 filename.txt
# Display last 1 kilobyte of a file
tail -c 1K large_file.dat
# Display last 1 megabyte of a file
tail -c 1M very_large_file.bin
Shows the last 200 bytes of the file.
View the End of Multiple Files
tail -v file1.txt file2.log-v(verbose) adds filename headers for clarity.
Suppress Filename Headers
tail -q file1.txt file2.txt-q(quiet) hides filenames when viewing multiple files.
Pipe Output from Another Command
ls -l /etc | tail -n 5
Lists files in /etc and shows the last 5 entries.
Save the Last Few Lines to a File
tail -n 10 app.log > last_errors.txt
Saves the last 10 lines of app.log into last_errors.txt.
Combine with head to Extract Middle Sections
head -30 file.txt | tail -n 10
Extracts lines 21–30 of file.txt (first 30 via head, then last 10 via tail).
Key Notes:
- Real-Time Monitoring: Use
-ffor live logs (e.g.,tail -f /var/log/syslog). - Log Rotation: Prefer
-Fover-fif logs are rotated (e.g., bylogrotate). - Large Files: Efficient for massive files since it doesn’t load the entire content.