Bash: Getting Help

man = manual

Comprehensive documentation for:
- Commands
- System calls
- Library functions
- File formats
- Configuration files

Installed locally on every Linux system

man command_name

man ls
man grep
man chmod
man passwd

man ls

Space       # Next page
b           # Previous page
Enter       # Next line
k           # Up one line
j           # Down one line
g           # Go to beginning
G           # Go to end
/pattern    # Search forward
?pattern    # Search backward
n           # Next search result
N           # Previous search result
q           # Quit
h           # Help

man grep

# Inside man page:
/regex      # Search for "regex"
n           # Next occurrence
n           # Next occurrence
q           # Quit

NAME
    Command name and brief description

SYNOPSIS
    How to use the command (syntax)

DESCRIPTION
    Detailed explanation

OPTIONS
    All available options/flags

EXAMPLES
    Usage examples (if available)

SEE ALSO
    Related commands

AUTHOR
    Who wrote it

BUGS
    Known issues

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

Syntax:
[]      = Optional
...     = Can be repeated
|       = OR (choose one)
<>      = Required (sometimes)

ls [OPTION]... [FILE]...
= ls
= ls -l
= ls -lah /etc /var
All valid!

cp [OPTION]... SOURCE DEST
= cp file.txt backup.txt

grep [OPTION]... PATTERN [FILE]...
= grep "error" log.txt
= grep -r "password" /etc

1. User commands (programs)
2. System calls (kernel functions)
3. Library functions (C library)
4. Device files
5. File formats and conventions
6. Games
7. Miscellaneous
8. System administration commands
9. Kernel routines

# Section 1: passwd command (change password)
man 1 passwd

# Section 5: passwd file format
man 5 passwd

# List all sections with keyword
man -k passwd
# Or: apropos passwd

# Without section number:
man passwd
# Shows first match (usually section 1)

# With section number:
man 5 passwd
# Shows file format of /etc/passwd

# This matters when multiple entries exist!

# Find commands with keyword in name
man -k keyword

# Or use apropos (same thing)
apropos keyword

man -k network
man -k compress
man -k encrypt
apropos ssh

# Open man page
man command

# Press / to search
/search_term

# Press n for next occurrence
# Press N for previous occurrence

# Search descriptions
man -K search_term

# This searches content, not just names
# Can be slow!

ls --help
grep --help
chmod --help
nmap --help

$ ls --help
Usage: ls [OPTION]... [FILE]...
List information about the FILEs (the current directory by default).

Mandatory arguments to long options are mandatory for short options too.
  -a, --all                  do not ignore entries starting with .
  -A, --almost-all           do not list implied . and ..
  -l                         use a long listing format
  -h, --human-readable       with -l, print sizes in human readable format
...

python3 -h
git -h
docker -h

help cd
help alias
help export
help source

# Check if command is built-in
type cd
# Output: cd is a shell builtin

type ls
# Output: ls is /usr/bin/ls

# Built-ins use 'help'
# External commands use 'man' or '--help'

Alternative to man pages
More structured (hyperlinked)
GNU project documentation
More detailed than man pages (sometimes)

info command

info ls
info grep
info bash

Space       # Next page
Backspace   # Previous page
n           # Next node
p           # Previous node
u           # Up one level
l           # Last visited node
q           # Quit
?           # Help

man page too brief? → Try info
Need comprehensive guide? → info
Want hyperlinked navigation? → info

Most people prefer man pages, but info can be more detailed.

Community-driven simplified man pages
Focuses on practical examples
Quick reference
Easy to read

# Node.js version
sudo npm install -g tldr

# Python version
pip3 install tldr

# Rust version (recommended)
cargo install tealdeer

tldr command

tldr tar
tldr grep
tldr find
tldr nmap

$ tldr tar

  tar
  Archiving utility.

  - Create an archive from files:
    tar cf target.tar file1 file2 file3

  - Extract an archive:
    tar xf source.tar

  - Extract a gzipped archive:
    tar xzf source.tar.gz

  - Create a gzipped archive:
    tar czf target.tar.gz file1 file2 file3

tldr --update

# 1. Try --help first (fast)
command --help

# 2. If not enough, check man page
man command

# 3. Still confused? Check examples
tldr command

# 4. Need more? Search online

# Don't know the command?
# Search by keyword

man -k network
man -k copy
man -k archive
apropos encrypt

# Find examples in man page
man grep
# Press / 
# Type: EXAMPLE
# Press n to find examples section

# Or use tldr for instant examples
tldr grep

Linux man pages online:
https://man7.org/linux/man-pages/

GNU Manuals:
https://www.gnu.org/manual/

The Linux Documentation Project:
https://tldp.org/

ExplainShell:
https://explainshell.com/
Paste command → Get explanation of each part

Example: https://explainshell.com/explain?cmd=tar+xzvf+file.tar.gz

DevHints:
https://devhints.io/

Cheat.sh (CLI):
curl cheat.sh/command

Example:
curl cheat.sh/tar
curl cheat.sh/grep

Stack Overflow:
https://stackoverflow.com/questions/tagged/bash

Unix & Linux Stack Exchange:
https://unix.stackexchange.com/

Reddit:
r/linux4noobs
r/commandline

# Create notes directory
mkdir -p ~/notes

# Create command cheat sheet
nano ~/notes/commands.md

# Add commands you use frequently
# Example:
# find . -name "*.txt"  # Find all txt files
# grep -r "pattern" /path  # Recursive grep

# View recent commands
history | tail -20

# Search history
history | grep nmap

# Save important commands
history | grep nmap >> ~/notes/nmap-commands.txt

alias note='nano ~/notes/commands.md'
alias notes='cat ~/notes/commands.md'

source ~/.bashrc

# Add note
note

# View notes
notes

# 1. Read the man page for 'ls'
man ls

# 2. Search for "sort" within the page
/sort

# 3. Find all commands related to "compress"
man -k compress

# 4. View the passwd file format
man 5 passwd

# 5. Compare with passwd command
man 1 passwd

# Try --help on various commands
grep --help
find --help
tar --help
ssh --help

# For built-ins, use help
help cd
help alias
help export

# Install tldr
sudo npm install -g tldr
# Or: pip3 install tldr

# Try it
tldr tar
tldr find
tldr rsync
tldr curl

# Scenario: Need to change file permissions
man -k permission

# Scenario: Need to archive files
man -k archive

# Scenario: Need to monitor network
man -k network | grep monitor

# Quick summary
command --help

# Detailed info
man command

# Examples
tldr command

# Search in man page
man command
/option_name

# Example: What does grep -r do?
man grep
/-r

# Search by keyword
man -k keyword
apropos keyword

# Example: Need to find files
man -k find

# Check history
history | grep partial_command

# Or search all commands
compgen -c | grep partial

Don't just skim!
- Try examples as you read
- Experiment with options
- Take notes

Don't memorize everything!
Focus on:
- Most frequently used options
- Options relevant to your work
- Building blocks (grep, find, etc.)

Best way to learn:
1. Have a problem
2. Look up solution
3. Try it
4. Understand what happened
5. Repeat

Don't just memorize commands
Understand:
- What problem does it solve?
- How does it work?
- When should I use it?

Getting Help:
man command          # Full manual
command --help       # Quick help
help command         # For built-ins
info command         # GNU info pages
tldr command         # Simple examples

Searching:
man -k keyword       # Search by keyword
apropos keyword      # Same as man -k
man -K pattern       # Search all content
/pattern             # Search within man page

Man Page Sections:
man 1 cmd            # User commands
man 5 file           # File formats
man 8 cmd            # Admin commands

Navigation (in man):
Space                # Next page
q                    # Quit
/pattern             # Search forward
n                    # Next result

Online:
https://explainshell.com
curl cheat.sh/command
https://man7.org/linux/man-pages/

man man              # Manual for man command
man intro            # Introduction to commands
man hier             # Filesystem hierarchy