How to get command Help under Linux

I. Classification of Linux system commands:

The commands for the Linux system are divided into internal commands and external commands: The internal command is the Linux Shell's own command, and the so-called external command means that the command itself has an executable program located in a directory on the filesystem.

Two. How the Linux command gets help:

There are help, man, info, official documents of the program, official documents, Google, Baidu.

Three. How to get help specifically:

1. Internal command: The internal command can generally get the method through the help command:

Format: Help COMMAND

2. External command: External commands can generally be obtained by using the Help, man, and info commands:

Format: COMMAND--help/-h

Man n COMMAND #n表示1-8 number

Info COMMAND

Detailed description of the 3.man command:

(1) man's configuration file location:/etc/man.config; You can search for a location by modifying Manpath: Specify the man help manual.

(2) manual page storage location:/usr/share/man/ where man1-man8 represents a different manual page, you can get a command with the Whatis command which help manuals and locations to help the document exist natively in the form of a compressed package:

man1: User Commands

Man2: System call

MAN3:C Library Call

MAN4: Equipment files and special files

MAN5: Configuration file format

Man6: Games

Man7: Remainder

MAN8: Commands for managing classes

(3) The parentheses in the command in the Help manual explain:

[]: Optional

<>: Required

A|b:a or B

...: The same content can appear multiple times

(4) The internal operation details of the man command:

Space, Ctrl+v,ctrl+f,ctrl+f: Turn one page at the end of a file

B, Ctrl+b: Turn to the file header page

D,ctrl+d: Turn half page at the end of the file

U,ctrl+u half page to file header

Return, CTRL + N, E, Ctrl+e, J, Ctrl+j: Flip a line to the end of the file

Y, Ctrl+y, K, Ctrl+k, Ctrl+p

Q: Indicates exit

#: View the first few lines of content

G: View the tail of the file

1g: Back to file header

Text Search:

/keyword: Searches the end of the file from the current position with the keyword specified character as the keyword;

N: Next keyword

N: previous keyword

Keyword: Searches for the file header from the current position with the keyword specified character as the keyword;

N: Next

N: Previous

4. Help documentation for the program itself:

The Help document for the program itself exists on this machine:/usr/share/doc/command-version

5. Other ways to help:

(1) Redhat Official document: Www.redhat.com/docs

http://slideshare.net/

(2) can be through Google, Baidu and other search engines, on the other hand can see a number of technical Daniel Blog.

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How to get command Help under Linux