The Linux Survival Guide: How to Get Help from the Command Line

In the world of Linux and Unix, you don’t need to memorize every flag and argument. You just need to know how to find them. Whether you are troubleshooting a production server or building a new Terraform module, these built-in help systems are your best friends.

1. The Manual Pages (man)

The man command is the gold standard for Linux documentation. Most programs install a manual page that describes their purpose, syntax, and options.

• Usage: man <command>
• Example: man tar

Pro Tip: Use /search_term while inside a man page to find specific keywords quickly. Press n to jump to the next result.

2. The help Built-in

Not every command is a standalone program; some are built directly into your shell (like cd, alias, or export). For these, man might not give you what you need.

• Usage: help <command>
• Example: help cd

3. The --help Flag

If you just need a quick syntax reminder without scrolling through a full manual, most modern CLI tools support the --help flag.

• Example: grep --help

4. whatis and apropos

• whatis: Gives you a one-line description of what a command does.

• apropos: Searches the manual page descriptions for a specific keyword. This is perfect when you know what you want to do, but not which command does it.

• Example: apropos "partition" (will list all commands related to disk partitioning).

5. GNU Info Pages (info)

For more complex GNU tools (like gcc or sed), the info system provides a more detailed, hyperlinked manual than man.

• Usage: info <command>

6. Understanding Manual Sections (Section 5)

The manual is divided into sections. By default, man shows you Section 1 (Executable programs). However, as a SysAdmin, you often need Section 5, which covers File Formats and Configurations.

If you run man passwd, you get help for the command to change a password. If you run man 5 passwd, you get the documentation for the actual file structure of /etc/passwd.

• Usage: man <section_number> <topic>
• Example: man 5 shadow or man 5 exports

Common Sections Reference:

1. Section 1: User Commands (e.g., ls, mkdir)
2. Section 5: File Formats (e.g., /etc/hosts, config files)
3. Section 8: System Administration commands (e.g., iptables, fdisk)

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Summary Table

Tool	Best Used For…
man	Full, detailed official documentation.
help	Shell built-in commands (Bash/Zsh).
–help	Quick syntax and flag reference.
apropos	Finding a command based on a keyword.
info	Deep-dives into GNU software.