Finding Help

Part of Essentials

This article covers how to learn and look up commands. If you're trying to find documentation about a specific system you've been handed (configs, logs, git history), see Finding Documentation in Day One.

You're on a server that's behaving unexpectedly. You find a command in a runbook that you've never used before — or you know the command but can't remember which flag does what you need. You could open a browser and search, but you're SSH'd into a server with no GUI, or the internet connection is locked down, or you're just faster when you don't leave the terminal.

The engineers who move fastest in Linux don't have better memory. They have a reliable lookup sequence that works offline, on any system, in under 30 seconds. This article gives you that sequence.

Where You've Seen This

If you've used PowerShell, you know Get-Help. In Windows CMD, it's command /?. On Linux, the equivalent is man, and it's more powerful — but also more intimidating until you know how to navigate it efficiently.

The --help flag is essentially universal: it works in Python CLIs, Docker, kubectl, git, virtually every well-built command-line tool. You've already used it. The difference here is learning to use man for the cases where --help isn't enough, and apropos for when you don't know the command name at all.

Every Linux system ships with complete documentation for every installed command. No internet required. Once you know how to navigate it, you're self-sufficient anywhere.

Choosing Your Source

graph TD
    A[I need help with a command] --> B{How much do I need?}
    B -->|One-line summary| C["whatis\nQuick description"]
    B -->|Remind me of the flags| D["command --help\nFast flag reference"]
    B -->|Show me examples| E["tldr\nPractical examples"]
    B -->|Full reference| F["man\nComplete documentation"]
    B -->|I don't know the command name| G["man -k / apropos\nKeyword search"]

    style A fill:#d69e2e,stroke:#cbd5e0,stroke-width:2px,color:#000
    style C fill:#2d3748,stroke:#68d391,stroke-width:2px,color:#fff
    style D fill:#2d3748,stroke:#68d391,stroke-width:2px,color:#fff
    style E fill:#2d3748,stroke:#63b3ed,stroke-width:2px,color:#fff
    style F fill:#2d3748,stroke:#fc8181,stroke-width:2px,color:#fff
    style G fill:#2d3748,stroke:#d69e2e,stroke-width:2px,color:#fff

The Tools

--help — Fastest Flag Reference

Why it matters: When you remember a command exists but can't recall a specific flag, --help is the fastest lookup. It prints directly to your terminal — no pager, no navigation required.
Using --help
```
find --help
grep --help
systemctl --help
```
Key insight: --help output is designed to be scanned, not read top-to-bottom. Look for the flag you need and move on. For commands where --help doesn't work, try -h.
When --help is Too Long
```
find --help | grep "\-name"     # filter for the flag you need
find --help | less              # page through it
```
whatis — One-Line Summaries

Why it matters: whatis gives you a single-line description of any command — useful when you encounter something unfamiliar and need to know what it does before going further.
Using whatis
```
whatis find
# find (1)              - search for files in a directory hierarchy

whatis chmod
# chmod (1)             - change file mode bits

whatis passwd
# passwd (1)            - change user password
# passwd (5)            - password file
```
Key insight: When whatis shows multiple results (like passwd above), the number in parentheses is the man page section. Section 1 is user commands; section 5 is file formats. You'll see how to use sections in the man section below.
man — Complete Documentation

Why it matters: Man pages are the authoritative reference for every command on the system. They cover every option, describe behavior edge cases, and are always accurate for the exact version installed.
Reading Man Pages
```
man find
man chmod
man 5 passwd    # section 5: the /etc/passwd file format
man hier        # the filesystem hierarchy standard
```
Key insight: Most people open a man page and feel overwhelmed. The next section covers how to read them efficiently without drowning in text.
tldr — Practical Examples First

Why it matters: tldr (Too Long; Didn't Read) shows common real-world examples for a command. It's community-maintained and cuts straight to the patterns you'll actually use.
Using tldr
```
tldr find
# find
# Find files or directories under the given directory tree, interactively.
#
# Find files by extension:
#   find root_path -name '*.ext'
#
# Find files matching multiple path/name patterns:
#   find root_path -name '*.ext' -or -name '*.py'
```
Installing tldr:
Install tldr
```
# On RHEL/Fedora
pip install tldr

# On Ubuntu/Debian
apt install tldr
tldr --update   # download the page cache
```
Key insight: tldr is excellent for commands you use occasionally and can never quite remember the exact syntax for. It's faster than man pages for practical lookups.

Reading Man Pages Effectively

Most people find man pages intimidating because they try to read them linearly. Don't. Man pages are reference documents — use them like a dictionary, not a novel.

The Structure of a Man Page

Every man page follows roughly the same structure:

Open a Man Page

man tar

Section	What It Contains	When to Read It
NAME	Command name and one-line description	Confirm you have the right page
SYNOPSIS	All usage patterns in compact notation	Find the pattern matching your use case
DESCRIPTION	What the command does, detailed	When you need to understand behavior
OPTIONS	Every flag explained	When you know the flag name
EXAMPLES	Real usage examples	Usually the fastest path to an answer
FILES	Configuration files and paths	When you need to find related files
SEE ALSO	Related commands	When this isn't quite what you needed

Reading the SYNOPSIS

The SYNOPSIS is the most information-dense part of a man page. It uses a compact notation:

Example SYNOPSIS from man find

find [-H] [-L] [-P] [-D debugopts] [-Olevel] [starting-point...] [expression]

[-H] — optional argument (square brackets = optional)
... — can be repeated
starting-point — required argument (no square brackets)
| — choose one of these options (when present)

You don't need to read every option in the SYNOPSIS. Scan it to understand the basic shape: what's required, what's optional, what comes first.

Navigating Inside man

Navigation Shortcuts Inside man

/keyword        # search for "keyword" forward
?keyword        # search for "keyword" backward
n               # jump to next search match
N               # jump to previous match
q               # quit
Space           # page down
b               # page up
G               # jump to end of page
g               # jump to beginning

The fastest workflow: Open the man page, press / and search for the flag or topic you need, press n to cycle through matches, press q when done.

Practical Example: Finding the -exec Flag in man find

man find
# Press: /-exec
# Press: n to cycle through results
# Found it — read the description, press q to quit

Man Page Sections

Man pages are divided into numbered sections. The same name can appear in multiple sections with different meanings:

Section	Contents
1	User commands (`ls`, `grep`, `find`)
2	System calls (`read`, `write`, `fork`)
3	Library functions (C standard library)
4	Device files (`/dev/null`, `/dev/sda`)
5	File formats (`/etc/passwd`, `/etc/fstab`)
6	Games
7	Miscellaneous (`regex`, `signal`, `man` conventions)
8	System administration (`mount`, `iptables`, `useradd`)

Specifying Man Page Sections

man passwd        # defaults to section 1: the passwd command
man 5 passwd      # section 5: the /etc/passwd file format
man 8 useradd     # section 8: the useradd system administration command

When you see a reference like passwd(5) in documentation, that means section 5 of the man page for passwd.

Searching When You Don't Know the Command

You know what you want to do but not which command does it. Two tools help:

Keyword Search Across All Man Pages

man -k "disk usage"
# df (1)                   - report file system disk space usage
# du (1)                   - estimate file space usage
# ncdu (1)                 - ncurses disk usage

apropos "network interface"
# ifconfig (8)             - configure a network interface
# ip (8)                   - show / manipulate routing, netns, devices, ...
# netstat (8)              - Print network connections, routing tables, ...

man -k and apropos are identical — they search man page descriptions by keyword. The output is command (section) — description.

Full-Text Search Across All Man Pages

man -K "TCP_NODELAY"    # capital -K: searches full text (slow but comprehensive)

-K (capital) searches the full text of every man page. It's slow, but useful when you know a specific term and want to find which commands or files use it.

info Pages

Some GNU utilities (like bash, gawk, grep) have info pages in addition to man pages. Info pages are often more detailed and better organized for linear reading:

Using info Pages

info bash       # the full Bash reference manual
info grep       # grep's info documentation
info coreutils  # documentation for ls, cp, mv, and other coreutils

Info uses its own navigation: n for next node, p for previous, u for up a level, q to quit. It's more like a book than a reference page.

When to Use info vs man

Most engineers use man for quick lookups because it's faster to navigate. info is worth reading for commands you use heavily and want to understand deeply — especially bash, which has an excellent info manual.

When Built-in Help Isn't Enough

Sometimes the man page doesn't have an example for your exact situation, or you're dealing with a tool that has sparse documentation. Reliable online sources:

Distro-Specific DocumentationUniversal ReferencesCommunity Resources

For questions about your specific distribution:

Red Hat / RHEL / Fedora: access.redhat.com/documentation — authoritative, deeply detailed
Ubuntu / Debian: ubuntu.com/server/docs and debian-handbook.info
Arch Linux Wiki: wiki.archlinux.org — excellent reference even for non-Arch systems

The Arch Wiki Secret

The Arch Linux Wiki is widely considered the best Linux documentation on the internet — even if you're running RHEL or Ubuntu. The concepts are universal even when the package names differ.

For command syntax, system calls, and file formats:

man7.org — every Linux man page online, cross-referenced and searchable
explainshell.com — paste any command and get a visual explanation of each part
GNU Coreutils Manual — gnu.org/software/coreutils/manual — authoritative docs for ls, cp, mv, find, and more

When you have a specific error or unusual situation:

Stack Overflow / Unix & Linux Stack Exchange — searching the error message often finds a direct answer
GitHub Issues — for open source tools, project issues often document edge cases not in the man page
Vendor documentation — for products like nginx, PostgreSQL, Docker — always more detailed than man pages

Quick Reference

Help Tool Selection

What You Need	Command	Speed
"What does this command do?"	`whatis command`	Instant
"What flags are available?"	`command --help`	Instant
"Show me common examples"	`tldr command`	Instant
"Full documentation"	`man command`	Opens pager
"Which section of man?"	`man whatis command`	Instant
"I don't know the command name"	`man -k keyword` or `apropos keyword`	Fast
"Find a specific term anywhere"	`man -K term`	Slow (full text)
"GNU tool deep dive"	`info command`	Opens pager

Key	Action
`/keyword`	Search forward
`?keyword`	Search backward
`n`	Next match
`N`	Previous match
`Space`	Page down
`b`	Page up
`G`	End of page
`g`	Beginning of page
`q`	Quit

Practice Exercises

Exercise 1: Efficient man Page Lookup

You need to use tar to extract a .tar.gz file but can't remember the exact flags. Use man tar to find the answer in under 30 seconds without reading the whole page.

Solution

Finding tar Extract Syntax

man tar
# Press: /extract
# Or press: /EXAMPLES (look for examples section)
# Or press: /-xzf (if you remember part of the syntax)

The flags for extracting a .tar.gz file:

tar Extract

tar -xzf archive.tar.gz         # extract gzip-compressed tar
tar -xzf archive.tar.gz -C /dest/  # extract to specific directory

-x = extract, -z = gunzip, -f = filename follows

Exercise 2: Finding the Right Command

You need to convert text to uppercase but you don't know which Linux command does this. Use man -k to find it.

Solution

Finding a Command by Description

man -k "uppercase"
# tr (1) - translate or delete characters

man -k "case conversion"
# awk (1p) - ...
# tr (1) - translate or delete characters

The command is tr:

Converting to Uppercase with tr

echo "hello world" | tr '[:lower:]' '[:upper:]'
# HELLO WORLD

Exercise 3: Man Page Sections

The command man crontab shows one page, but there's also a crontab(5) that documents the file format. Open the file format documentation.

Solution

Opening a Specific Man Page Section

man crontab      # section 1: the crontab command
man 5 crontab    # section 5: the crontab file format

# Check which sections exist
whatis crontab
# crontab (1)  - maintain crontab files for individual users
# crontab (5)  - tables for driving cron

Quick Recap

--help — fastest way to see flags; pipe to grep or less when it's too long
whatis — one-line description; shows available man page sections
tldr — community examples; install it if it's not there
man — complete reference; navigate with /keyword not by reading top to bottom
man -k / apropos — search when you don't know the command name
Man sections — man 5 passwd accesses file formats; man 8 useradd accesses admin commands
Arch Wiki — the best Linux documentation on the internet for any distribution

What's Next?

You can find any command, look it up efficiently, and get unstuck fast. Now it's time to understand the structure that underlies everything else in Linux: file permissions.

Head to File Permissions to learn how Linux controls who can read, write, and execute files — and how to manage permissions confidently without locking yourself (or your team) out.

Finding Help

Where You've Seen This

Choosing Your Source

The Tools

Reading Man Pages Effectively

The Structure of a Man Page

Reading the SYNOPSIS

Navigating Inside man

Man Page Sections

Searching When You Don't Know the Command

info Pages

When Built-in Help Isn't Enough

Quick Reference

Help Tool Selection

man Page Navigation

Practice Exercises

Quick Recap

Further Reading

Command References

Deep Dives

Official Documentation

What's Next?