head

The head command displays the beginning of a file or input stream. It is useful for checking headers, previewing structured data, or sampling output without printing everything.

Displaying the First Ten Lines

With no count option, head prints the first 10 lines of each named file:

$ head events.log

The file is not modified. If it contains fewer than 10 lines, all available lines are printed.

CheckWhat does head events.log print by default?

The last 10 lines, or all lines if the file is shorter. The first 10 lines, or all lines if the file is shorter. Only the first line, regardless of the file length.

Choosing a Line Count

Use -n NUMBER to choose how many lines to print:

$ head -n 15 events.log

GNU head also accepts the compact form -15, but -n 15 states the option's meaning more clearly.

CheckWhich command displays the first five lines of report.txt?

head -c 5 report.txt head -n 5 report.txt tail -n 5 report.txt

Choosing a Byte Count

Use -c NUMBER when you need bytes rather than complete lines:

$ head -c 20 archive.bin

This prints the first 20 bytes. The output may end in the middle of a text line or, for multibyte text, in the middle of an encoded character. Use line mode for ordinary text previews.

CheckWhich command writes the first 100 bytes of payload.bin to stdout?

head -c 100 payload.bin head -n 100 payload.bin cut -c 100 payload.bin

Reading stdin and Multiple Files

When no file operand is supplied, head reads stdin:

$ generate-report | head -n 5

When several files are named, head normally adds a header identifying each file's output:

$ head -n 2 january.txt february.txt
==> january.txt <==
...

==> february.txt <==
...

Use -q to suppress these headers or -v to show a header even for one file.

CheckIn generate-report | head -n 5, what does head read?

The stdout of generate-report through stdin. The first five filenames in the current directory. Five bytes from a file named generate-report.

CheckWhich option suppresses filename headers when head reads several files?

-v -c -q

To practice previewing file beginnings, try these hands-on labs:

1. Linux head Command: File Beginning Display - This lab will guide you through using the head command to display the initial lines of text files, including modifying the line count.
2. Viewing Log and Configuration Files in Linux - Practice essential Linux command-line skills for efficiently viewing and navigating text files, including system logs and configuration files, which often require commands like head.
3. Rapid Threat Detection - Apply your knowledge of head (and tail) to quickly extract and analyze recent log entries, simulating real-world cybersecurity analysis.

Summary

You can now preview the beginning of files and command output with head.

1. Use the default first-ten-line view.
2. Select a line count with -n.
3. Select a byte count with -c when appropriate.
4. Read from stdin in a pipeline.
5. Control headers when several files are shown.