Display reference manuals for Linux commands
The man command is the primary interface used to read the system's reference manuals (man pages). These pages provide detailed information about commands, configuration files, system calls, and library functions.
man [OPTION]... [SECTION] PAGE...
-a：Search all manual sections for the specified keyword.
-f：Equivalent to the `whatis` command; display a short description of the keyword.
-P <pager>：Specify the pager to use for displaying output (e.g., `less`).
-M <path>：Specify the search path for manual pages.
Manual pages are organized into sections:
1：Executable programs or shell commands.
2：System calls (functions provided by the kernel).
3：Library calls (functions within program libraries, e.g., libc).
4：Special files (usually found in /dev).
5：File formats and conventions (e.g., /etc/passwd).
6：Games.
7：Miscellaneous (including macro packages and conventions, e.g., man(7), ascii(7)).
8：System administration commands (usually only for root).
9：Kernel routines (non-standard).
Running man ls will show "LS(1)" in the top corner, indicating that ls is in Section 1 (User Commands). Running man ifconfig will show "IFCONFIG(8)", indicating Section 8 (System Administration).
man searches sections in numerical order. For example:
man sleep
This usually displays the sleep command (Section 1). To view the sleep library function, specify Section 3:
man 3 sleep
tldr: A simplified, community-driven manual that provides practical examples instead of exhaustive documentation.