
Help and Man Commands
Think of help
and man
as your built-in Linux cheat sheets. When you're not sure how to use a command or need to look up its options, these commands are your best friends. They're like having a Linux expert right at your fingertips!
Quick Reference
Command | Description | Common Use |
---|---|---|
help |
Show help for built-in shell commands only | Quick reference for commands like cd, echo, pwd |
man |
Show detailed manual pages for non-built-in commands | Complete documentation for commands like ls, grep, cat |
help Command
The help
command is like a quick reference guide for built-in shell commands. It's perfect when you need a fast reminder of how to use commands like cd
, echo
, or pwd
.
When to Use help
Use help
when you want to:
- Quickly check how to use a built-in command
- See available options for shell commands
- Get a brief overview of command syntax
- Find basic usage examples
How to Tell if a Command is Built-in
To check if a command is built into the shell, you can use:
# Check if cd is a built-in command
type cd
# Output: cd is a shell builtin
# Check if ls is a built-in command
type ls
# Output: ls is /bin/ls # This means it's not built-in
Remember: If a command is built-in, use help
. If it's not built-in, use man
.
Common Options
Option | What It Does | When to Use It |
---|---|---|
-d |
Show brief description | When you just need a quick summary |
-m |
Show man-page style format | When you want more detailed help |
-s |
Show short usage summary | When you just need the basic syntax |
Practical Examples
Basic Usage
# Get help for cd command
help cd
# Get brief description
help -d echo
# Get usage summary
help -s pwd
Sample Output (for help cd)
# help cd output
cd: cd [-L|[-P [-e]] [-@]] [dir]
Change the shell working directory.
Options:
-L force symbolic links to be followed
-P use the physical directory structure
-e if the -P option is supplied, and the current working directory
cannot be determined successfully, exit with a non-zero status
-@ on systems that support it, present a file with extended attributes
as a directory containing the attributes
man Command
The man
command is like having a complete Linux manual at your fingertips. It provides detailed documentation for almost any command, including examples, options, and related commands.
When to Use man
Use man
when you want to:
- Get complete documentation for a command
- See detailed examples and options
- Learn about related commands
- Understand command behavior in depth
- Find information about file formats or system calls
Common Options
Option | What It Does | When to Use It |
---|---|---|
-k |
Search for keywords | When you're not sure which command to use |
-f |
Show brief description | When you need a quick summary |
-a |
Show all matching pages | When a command has multiple manual pages |
-w |
Show file location | When you need to know where the man page is stored |
-K |
Search in all man pages | When you need to find text across all manuals |
-l |
List manual pages | When you want to see all available man pages |
-P |
Use specific pager | When you want to use a different viewer |
Understanding Man Page Sections
Man pages are organized into numbered sections, each covering a different type of documentation. Not all commands will have pages in all sections - some might only appear in one section, while others (like passwd
) might appear in multiple sections with different meanings.
Section | What It Contains | Example | Notes |
---|---|---|---|
1 | User commands | man 1 ls |
Most common section for everyday commands |
2 | System calls | man 2 open |
Functions provided by the kernel |
3 | Library functions | man 3 printf |
Programming library functions |
4 | Special files | man 4 null |
Device files in /dev |
5 | File formats | man 5 passwd |
Configuration file formats |
6 | Games | man 6 fortune |
Games and amusements |
7 | Miscellaneous | man 7 ascii |
Various topics and conventions |
8 | System admin | man 8 shutdown |
Commands for system administration |
How to Check Available Sections
To see which sections a command appears in, use the -f
option:
# Check all sections for passwd
man -f passwd
# Output might show:
# passwd (1) - change user password
# passwd (5) - password file
Practical Examples
Basic Usage
# View manual for ls command
man ls
# Search for commands about files
man -k file
# View specific section
man 1 passwd
# Search all man pages for a term
man -K "regular expression"
# List all man pages
man -l
Navigation Tips
Key | What It Does | When to Use It |
---|---|---|
Space or f |
Move forward one page | When you want to read more |
b |
Move back one page | When you want to review previous content |
/pattern |
Search for text | When you're looking for specific information |
n |
Find next match | When you want to see more search results |
N |
Find previous match | When you want to go back to previous search results |
q |
Quit man page | When you're done reading |
h |
Show help | When you need to see all navigation options |
g |
Go to start | When you want to return to the beginning |
G |
Go to end | When you want to jump to the end |
Tips for Success
- Start with help: Use
help
for built-in commands first - Use man for details: When you need complete documentation
- Try -k for discovery: Great for finding related commands
- Learn the navigation: Practice using man page navigation keys
Common Mistakes to Avoid
- Using
help
for non-built-in commands - Forgetting to use
q
to quit man pages - Not checking multiple sections when a command exists in more than one
- Not using
-k
when you're not sure which command to use
Best Practices
- Use
help
for quick reference of built-in commands - Use
man
for complete documentation - Learn the man page navigation shortcuts
- Use
-k
to discover new commands