man Command
Display manual pages and documentation for Linux commands, system calls, and functions.
Syntax
man [OPTION]... [SECTION] PAGE...
man -k KEYWORD
man -f PAGE
The man command displays the manual pages (documentation) for commands, system calls, library functions, and configuration files in Linux systems.
Common Options
| Option | Description |
|---|---|
-k, --apropos |
Search manual page names and descriptions |
-f, --whatis |
Display short description of command |
-w, --where |
Show location of manual page files |
-a, --all |
Display all matching manual pages |
-u, --update |
Update manual page cache |
-P, --pager |
Specify pager program to use |
-H, --html |
Output in HTML format |
-t, --troff |
Format for printing |
Manual Page Sections
| Section | Description | Examples |
|---|---|---|
1 |
User commands | ls, cp, mv, grep |
2 |
System calls | open, read, write, fork |
3 |
Library functions | printf, malloc, strlen |
4 |
Device files | null, zero, random |
5 |
File formats | passwd, fstab, hosts |
6 |
Games | fortune, cowsay |
7 |
Miscellaneous | ascii, regex, signal |
8 |
System administration | mount, fsck, iptables |
Basic Examples
Viewing manual pages
# View manual for ls command
man ls
# View manual for specific section
man 5 passwd # passwd file format
man 1 passwd # passwd command
# View all matching pages
man -a printf # Show all printf manuals
# View manual in specific language
LANG=es_ES man ls
Display manual pages for commands and topics
Searching manual pages
# Search by keyword
man -k network
man -k "file system"
# Search with apropos (same as -k)
apropos copy
apropos "regular expression"
# Get short description
man -f ls
whatis ls # Same as man -f
# Search in specific section
man -k -s 1 copy
Search for manual pages by keywords and descriptions
Manual page information
# Show location of manual files
man -w ls
man --where passwd
# Show path for specific section
man -w 5 passwd
# List all manual paths
manpath
# Update manual database
sudo mandb
Get information about manual page locations and database
Navigating Manual Pages
Navigation Keys (in less pager)
- Space or Page Down - Next page
- b or Page Up - Previous page
- ↓ or j - Next line
- ↑ or k - Previous line
- g - Go to beginning
- G - Go to end
- /pattern - Search forward
- ?pattern - Search backward
- n - Next search result
- N - Previous search result
- h - Help
- q - Quit
Search within manual pages
# While viewing a manual page:
/search_term # Search forward for "search_term"
?search_term # Search backward for "search_term"
n # Go to next match
N # Go to previous match
# Case-insensitive search
/(?i)pattern # Search ignoring case
Search for specific content within manual pages
Advanced Usage
Output formatting
# Generate HTML output
man -H firefox ls
# Generate PostScript for printing
man -t ls | lpr
# Save manual as text file
man ls | col -b > ls_manual.txt
# Use different pager
man -P cat ls # Use cat instead of less
man -P "less -S" ls # Use less with specific options
Format manual pages for different output methods
Configuration and customization
# Set default pager
export PAGER=less
export MANPAGER="less -X"
# Set manual path
export MANPATH=/usr/share/man:/usr/local/share/man
# Configure less for better manual viewing
export LESS="-R -M -I -j.5"
# Set manual width
export MANWIDTH=80
Customize manual page display and behavior
Batch operations
# Generate manual index
sudo mandb
# Find all manuals containing keyword
man -k . | grep -i network
# List all available manual pages
man -k . | wc -l
# Find manuals in specific section
man -k . | grep "^.*([1-8])"
# Export manual to different formats
for cmd in ls cp mv; do
man $cmd | col -b > ${cmd}_manual.txt
done
Batch processing and management of manual pages
Manual Page Structure
Standard Sections
- NAME - Command name and brief description
- SYNOPSIS - Command syntax and options
- DESCRIPTION - Detailed description of functionality
- OPTIONS - Command-line options and arguments
- EXAMPLES - Usage examples
- FILES - Related files and directories
- SEE ALSO - Related commands and references
- BUGS - Known issues and limitations
- AUTHOR - Author information
Reading manual syntax
# Understanding synopsis notation:
command [OPTION]... FILE...
# [] = optional
# ... = can be repeated
# | = alternatives (or)
# {} = required group
# Examples:
ls [OPTION]... [FILE]... # ls with optional options and files
cp [OPTION]... SOURCE DEST # cp requires source and destination
grep [OPTION]... PATTERN [FILE]... # grep requires pattern
Understanding the syntax notation used in manual pages
Practical Examples
Learning new commands
# Discover commands for specific tasks
man -k "copy files"
man -k "text editor"
man -k "network"
# Learn about system calls
man 2 open
man 2 fork
man 2 execve
# Understand file formats
man 5 fstab
man 5 passwd
man 5 crontab
Use man to learn about new commands and system concepts
Quick reference
# Quick command lookup
whatis tar
whatis grep
whatis awk
# Find commands by functionality
apropos compress
apropos "regular expression"
apropos archive
# Get command location and manual
which ls && man ls
type -a python && man python
Quick reference and command discovery
Documentation workflow
# Create personal command reference
mkdir ~/manuals
man ls | col -b > ~/manuals/ls.txt
man grep | col -b > ~/manuals/grep.txt
# Search across multiple manuals
grep -r "regular expression" ~/manuals/
# Create command cheat sheet
echo "# Common Commands" > cheatsheet.md
for cmd in ls grep find; do
echo "## $cmd" >> cheatsheet.md
man $cmd | col -b | head -20 >> cheatsheet.md
done
Building personal documentation and reference materials
Troubleshooting
Common Issues
- No manual entry - Command not installed or no manual available
- Broken display - Terminal encoding or pager issues
- Missing sections - Development packages not installed
- Outdated cache - Manual database needs updating
Fixing manual issues
# Update manual database
sudo mandb
# Check manual paths
manpath
echo $MANPATH
# Install missing manual pages
sudo apt install man-db manpages-dev # Debian/Ubuntu
sudo yum install man-pages man-pages-devel # RHEL/CentOS
# Fix encoding issues
export LANG=en_US.UTF-8
export LC_ALL=en_US.UTF-8
# Reset pager settings
unset PAGER MANPAGER
Resolve common manual page display and access issues
Alternative documentation
# Use info pages
info ls
info grep
# Built-in help
ls --help
grep --help
# Online documentation
curl cheat.sh/ls
curl cht.sh/grep
# Local documentation
ls /usr/share/doc/
find /usr/share/doc -name "*.txt" -o -name "README*"
Alternative sources of command documentation