Vol. I · No. 46The command line sectionSat, 10 Oct 2026
Linux · system information

man

the manual, built in

man shows the reference manual for nearly every command on the system. It is installed with the command and matches the exact version you have — which a web search does not guarantee. It opens in less, so / searches and q quits.

Not sure what a switch does? man command, then /-x to jump to it.

Open
man ls
q to quit
Search inside
/word
n for the next match
Find a command
man -k word
searches the descriptions
Shorter help
command --help
a quick summary

At the terminal

Read the session first, then the notes: each numbered line in the output is answered by the note with the same number.

user@netflow — bashman-db
$ man ls
1LS(1) User Commands LS(1)
 
NAME
ls - list directory contents
2SYNOPSIS
ls [OPTION]... [FILE]...
3$ man -k "list directory"
dir (1) - list directory contents
ls (1) - list directory contents
4$ man 5 passwd
Illustrative session · names, sizes and dates are examples, and every address is from a documentation or private range
Reading the output

What the numbered lines are telling you

1
The header: name and section

The (1) is the section. Section 1 is user commands, 5 is file formats, 8 is administration commands.

2
The synopsis

How the command is written. Square brackets mark optional parts, and three dots mean "one or more".

3
Searching for a command by what it does

-k looks through the one-line descriptions of every page — for when you know the task but not the name.

4
Asking for a section

passwd is both a command and a file. man 5 passwd opens the page describing the format of /etc/passwd.

Switches

A switch changes how the command behaves. These are the ones used day to day; man man lists the rest. Single-letter switches can usually be joined, so -l -a may be written -la.

-k WORD
Search the descriptions of all pages for a word.
-f NAME
List the sections that have a page of this name.
NUM
A section number before the name: man 5 passwd.
-a
Show every matching page, one after another.

Variations worth knowing

The same tool, pointed at a narrower question. These four cover most of what it is reached for day to day.

ls --help

A short summary of options, printed straight to the terminal.

whatis tar

Prints just the one-line description.

man -f printf

Lists every section that has a page of that name.

tldr tar

Practical examples rather than a full reference — a separate package.

In cybersecurity

Reading the manual is how you find out what a pasted command will really do.

Look up switches before running

A command copied from a forum may contain an option you would not have chosen. Thirty seconds in the manual is cheaper than the mistake.

The local page is the accurate one

Options differ between versions and between Linux and macOS. man describes the program actually installed.

Read the security notes

Many pages have a section on security considerations — ssh, sudo and tar among them. It is where the sharp edges are documented.

Filed under

System information

Read alongside

whichPrints the full path of the program that a command name would run.historyLists the commands you have typed, numbered, so they can be searched and run again.