head — Clarus Command Guide

Install

# Most systems: head is part of GNU coreutils (usually already installed)
head --version

# RHEL / Alma / Rocky
sudo dnf install coreutils

# Debian / Ubuntu
sudo apt install coreutils

# openSUSE
sudo zypper install coreutils

# Arch
sudo pacman -S coreutils

What it does

head prints the beginning of a file or standard input. By default it shows the first 10 lines, but it can also show a chosen number of lines or bytes. It is one of the quickest ways to preview data without opening an editor or paging through the entire file.

How it works (mechanical)

Opens one or more files, or reads from standard input if no file is given.
Counts lines by default, or bytes when given the -c option.
Stops reading as soon as the requested amount has been printed.
Works very well in pipelines because it exits early once it has enough input.
When multiple files are named, it prints headers unless suppressed by options or single-file usage.

Quick Start

# Show the first 10 lines of a file
head myfile.txt

# Show the first 20 lines
head -n 20 myfile.txt

# Preview command output
dmesg | head

10 Practical Examples

Preview the top of a text file
```
head notes.txt
```
Show the first 25 lines
```
head -n 25 /etc/services
```
Show only the first 3 lines
```
head -n 3 inventory.csv
```
Preview the first 100 bytes of a file
```
head -c 100 binary.dat
```
Inspect the beginning of a log
```
head -n 15 /var/log/messages
```
Preview piped output
```
ps aux | head
```
Check a CSV header and first few rows
```
head -n 6 sales.csv
```
Show the first line only
```
head -n 1 /etc/hostname
```
Read from standard input interactively
```
cat largefile.txt | head -n 12
```
Preview several files at once
```
head file1.txt file2.txt
```

Notes & Gotchas

Default is 10 lines. If you need a different amount, use -n explicitly.
Use -c carefully on text. Bytes are not the same as characters in all encodings.
Binary files may look messy. head will still print raw bytes if asked.
Multiple-file output includes headers. That is helpful for comparison, but can surprise scripts.
Early exit can affect pipelines. Some upstream commands may notice a broken pipe when head stops reading.

Historical Context

head is a long-standing Unix utility built for fast inspection of files and streams. It remains a core part of GNU coreutils and is still one of the most commonly used commands in shell work because it is simple, predictable, and pipeline-friendly.

Modern Equivalent

sed -n '1,10p' — more flexible when selecting exact line ranges
awk 'NR<=10' — useful when preview and processing happen together
bat --paging=never file | head — prettier file preview when bat is installed

Related Commands

tail — show the end of a file
less — scroll through a file interactively
sed — stream editor for line selection and editing
awk — pattern scanning and field processing
wc — count lines, words, and bytes
cat — print full file contents
tee — split output to screen and file
nl — number lines of a file