Linux get help information for commands

To determine whether a command is built into Linux, you can use the Type command, and only the Linux built-in commands can be used to get help.
# Type cd
Output: CD is a shell builtin
Note that this command is a built-in command from the system, so you can use the help command to get assistance.

# Help Command name

< two >, external commands How to get help documents:

(1) The first option is to use--help

Format: # command name--help

Example: # mkdir--help

(2) You can use the man command to get complete help for a command

Format: # man command name
Example: # man mkdir
The man command is to invoke the less tool to display the document, and man's specific operation method is the same as less.

Common uses of Linux man: 
Man-section cmd:directlySpecify a Search man page in a specific section, such asMans 5 passwdHelp for direct access to file format version
man-a cmd:Openhelp with the same name in all sections, for example Man–a passwd, you will first enter a passwd (1) command version passwd Help, you press the Q key will enter passwd (5), passwd configuration file format Help
man-aw cmd:ShowAll cmd file paths for all manuals, such as Man-aw passwd is
/usr/share/man/man1/passwd.1.gz
/usr/share/man/man5/passwd.5.gz
man-m cmd:Specify the search path for the manual file, such as Man-m/home/mysql/man MySQL display is the help of your installed MySQL, not the system comes with the old version of MySQL help
Man cmd| col-b > Cmd.txt: Output man manual information to a text file

Man Simple introduction: 
The man in Linux is very powerful, and the manual is divided into sections, which can be used to specify a different section to navigate, with each section having the following meanings:

• 1 – User Commands General user command

• 2-system Calls system invoke command, such as Open,write (through this, at least it can be easily found to call this function, need to add what header file)

li>

3-c Libraries Functions C function library commands, such as Printf,fread

• 4-devices and special files are special files, which is the various device files under/dev &NB Sp

Man command format: 
Man [option] Name:name is generally the name of the Help document, corresponding to command name, function name, or configuration file name (with suffix!) ), such as
Man nsswitch.conf: View the Help documentation for the/etc/nsswitch.conf file
Man networks: View the Help documentation for the/etc/sysconfig/networks file

to view the help documentation for a specific language version:set the environment variable LANG=ZH_CN before executing the man query

Man 's configuration file/etc/man.config: 
If you don't want to specify the path with-M every time man cmd, you can modify the configuration file to add content such as
Manpath/home/mysql/man

Linux get help information for commands