Usages of tail and head

The commands tail and head, as their names suggest, respectively print the beginning and ending of files.

You can easily understand the usages of tail with this example: tail -n 50 /var/log/auth.log. This command shows last 50 lines of the auth.log file. And the usages of head are alike. There is only one basic and intuitive option.

Specifying Unit

You wanna lines? Use -n, and there are -c for characters, -b for bytes.

With this knowledge, you can print first 5 characters of a file with command: head -c 5 filename.

Special Usage of tail

To show a real-time output of a changing file, we can use the -f or --follow options: tail -f /var/log/auth.log prints the end of the file and updates the output when lines are appended to file.

It’s really helpful and handy when you debug your Linux system under some circumstances.

— Feb 14, 2019