Linux Man Pages: How to Teach Yourself Any Command

What Are Man Pages?

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Man pages (manual pages) are the built-in documentation system on Linux. Nearly every command, system call, library function, and configuration file has a man page explaining what it does, how to use it, and what options it accepts.

When you don’t know how a command works — or you know the command but forgot a specific flag — the man page is where you look first. It’s available offline, on any system, without a browser.

man ls

That opens the full manual entry for ls. You’re now reading documentation written by the people who built the tool.

Opening and Navigating Man Pages

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Man pages open in a pager — usually less. If you’ve used less before (or Vim), the navigation will feel familiar:

Searching within a man page

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If you’re looking for a specific option, search for it:

/--recursive

This jumps to the first occurrence. Press n to cycle through matches.

Man Page Sections

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Man pages are organized into numbered sections. This matters because the same name can exist in multiple sections with completely different meanings.

Why sections matter

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Consider crontab:

man crontab       # Section 1 — the crontab command (how to edit your crontab)
man 5 crontab     # Section 5 — the crontab file format (syntax of the schedule)

Or passwd:

man passwd        # Section 1 — the passwd command (changing passwords)
man 5 passwd      # Section 5 — the /etc/passwd file format (fields and structure)

Or printf:

man printf        # Section 1 — the shell printf command
man 3 printf      # Section 3 — the C library printf() function

If you open a man page and it’s not what you expected, you’re probably looking at the wrong section.

Specifying a section

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man 2 open        # The open() system call
man 3 sleep       # The C sleep() function (not the shell command)
man 5 fstab       # The fstab file format
man 8 mount       # The mount command (system administration)

Listing all available sections for a name

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man -f crontab
# crontab (1)          - maintain crontab files for individual users
# crontab (5)          - tables for driving cron

# Equivalent command:
whatis crontab

Structure of a Man Page

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Most man pages follow a standard layout:

Not every man page has every section, but NAME, SYNOPSIS, DESCRIPTION, and OPTIONS are almost always present.

Reading the SYNOPSIS

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The SYNOPSIS tells you how to invoke a command. It uses formatting conventions to show what’s required, what’s optional, and what can be repeated:

ls [OPTION]... [FILE]...

So ls [OPTION]... [FILE]... means:

• ls — the command itself (required)
• [OPTION]... — zero or more options (all optional)
• [FILE]... — zero or more filenames (optional; defaults to current directory)

A more complex example:

cp [OPTION]... SOURCE... DEST
cp [OPTION]... -t DIRECTORY SOURCE...

This shows cp has two forms. In the first, you provide one or more source files and a destination. In the second, you use -t to specify the target directory first.

Finding Man Pages

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apropos — Search by keyword

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When you don’t know the command name, search the man page descriptions:

apropos partition
# cfdisk (8)           - display or manipulate a disk partition table
# fdisk (8)            - manipulate disk partition table
# parted (8)           - a partition manipulation program
# sfdisk (8)           - display or manipulate a disk partition table

apropos "copy file"
# cp (1)               - copy files and directories
# install (1)          - copy files and set attributes

apropos searches the NAME section of all man pages. It’s equivalent to man -k:

man -k network

whatis — One-line description

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whatis grep
# grep (1)             - print lines that match patterns

whatis mount
# mount (2)            - mount filesystem
# mount (8)            - mount a filesystem

Updating the man page database

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apropos and whatis rely on a database. If they return nothing, update it:

sudo mandb

Practical Examples

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Find all man page sections for a command

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man -f open
# open (1)             - start a file in its preferred application
# open (2)             - open and possibly create a file

# Then read the one you need
man 2 open

Search for all pages about “firewall”

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apropos firewall
# firewalld (1)        - Dynamic Firewall Manager
# iptables (8)         - administration tool for IPv4 packet filtering
# nft (8)              - nftables command line tool

Read just a specific section of a man page

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Use the search feature. Open the man page and jump directly to EXAMPLES:

man rsync
# Then type:
/^EXAMPLES

The ^ anchors to the start of a line, so this finds the EXAMPLES heading.

View a man page for a config file

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man 5 sshd_config     # SSH server configuration options
man 5 resolv.conf     # DNS resolver configuration
man 5 fstab           # Filesystem mount table format
man 5 sudoers         # sudo configuration file

This is one of the most underused features. When you need to edit a config file and aren’t sure of the syntax, the section 5 man page has the authoritative reference.

man vs --help vs info

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You’ll encounter three documentation systems:

In practice, man is what you’ll use 90% of the time. --help is useful for a quick flag check without opening the pager. info has more detail for some GNU tools (like tar, coreutils) but most people never need it.

# Quick flag reminder
tar --help | grep "exclude"

# Full explanation with context
man tar

Controlling How Man Pages Display

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Open in a specific pager

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# Use less (default)
man ls

# Pipe to grep for quick searches
man ls | grep -A2 "\-t,"

Export a man page to plain text

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man ls | col -bx > ls-manual.txt

View a man page from a specific path

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man ./my-custom-tool.1

Section 2 and 3: For Developers

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If you write C programs or want to understand how Linux works at a lower level, sections 2 and 3 are essential:

man 2 fork            # How processes are created
man 2 execve          # How programs are launched
man 2 open            # How files are opened at the kernel level
man 2 socket          # How network sockets are created

man 3 malloc          # Memory allocation
man 3 strcmp           # String comparison
man 3 getenv          # Reading environment variables

These pages document the interface between your programs and the Linux kernel (section 2) or the C standard library (section 3). Even if you don’t write C, reading these helps you understand what’s happening beneath the shell commands you run daily.

Best Practices

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• Start with man command before searching the web — it’s faster, works offline, and is always accurate for your installed version
• Use man 5 filename when editing config files — the syntax reference is right there
• Use apropos keyword when you know what you want to do but not which command does it
• Check SEE ALSO at the bottom of man pages — it links to related tools and pages you might need
• Use man -f command to discover if a command exists in multiple sections
• Search within man pages with /pattern — don’t read top to bottom when you need one specific flag
• Read the SYNOPSIS carefully — it tells you the exact invocation syntax without guessing
• Run sudo mandb if apropos returns empty results — the database may need refreshing