Learn to use the view of Help files and learn basic commands by helping commands

Access to Linux command help:

Internal command:
# Help COMMAND
External command:
(1) Simple help with the command
# COMMAND--help
# command-h
(2) Command manual page
# Man [Chpater] KEYWORD
(3) Information page
# info COMMAND
(4) Help documentation for the program itself
README, INSTALL, change
(5) Documentation provided by the program
(6) Official documentation provided by the release version
Http://www.redhat.com/docs
(7) Google

Use of the Man Handbook:
/usr/share/man/
Man1, ..., man9
Man1: User command;
MAN2: System call;
MAN3:C library call;
MAN4: Equipment files and special documents;
MAN5: Configuration file format;
Man6: Game;
Man7: Miscellaneous;
MAN8: Management command;

The man may also store other paths:
Configuration file for man command:/etc/man.config
MANPATH

Man unzip its help manual to a temporary directory, and then calls the less command to display the contents of the file;

Paragraphs in the         Help manual:
             NAME
            Synopsis
             DESCRIPTION
             OPTIONS
             EXAMPLES
            AUTHOR
             See ALSO

Synopsis:
[]: Optional
<>: Required
A|b: Two Choose one
...: Similar content can appear multiple times

How to operate the man command:
Space: Turn a screen at the end of the file;
B: Turn the file to the first screen;
D: half-screen to the tail of the file;
U: Turn half screen to file header;
Return: Flip a line to the end of the file;
K or y: Flip a line to the file header;

#: Quick go to # line;
1 G: Return to the first line;
G: to the last line;

Q: Exit;

Exercise: 1. Get the use format of the date command:
Answer: Man date

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2. What is the day of the week?

Answer: Date +%a

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3. Set the current system time?

Date–s 16:24:30

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4. Set the current system date?

Date 08282015

650) this.width=650; "title=" image "style=" border-left-0px; border-right-width:0px; Background-image:none; border-bottom-width:0px; padding-top:0px; padding-left:0px; margin:0px; padding-right:0px; border-top-width:0px "border=" 0 "alt=" image "src=" http://s3.51cto.com/wyfs02/M01/72/4C/ Wkiol1xglaaikivjaaa3dmrryug955.jpg "width=" 244 "height=" "/>"

CentOS 7:timedatectl command to view and set the time?
Answer: 1) View time TIMEDATECTL status

650) this.width=650; "title=" image "style=" border-left-0px; border-right-width:0px; Background-image:none; border-bottom-width:0px; padding-top:0px; padding-left:0px; margin:0px; padding-right:0px; border-top-width:0px "border=" 0 "alt=" image "src=" http://s3.51cto.com/wyfs02/M01/72/4C/ Wkiol1xglaet5wroaabthzfxcvg341.jpg "width=" 244 "height=" 111 "/>

2) Set time Timedatectl set-time 19:30:20

650) this.width=650; "title=" image "style=" border-left-0px; border-right-width:0px; Background-image:none; border-bottom-width:0px; padding-top:0px; padding-left:0px; padding-right:0px; border-top-width:0px "border=" 0 "alt=" image "src=" http://s3.51cto.com/wyfs02/M01/72/4F/ Wkiom1xgk47ymjrxaabkpv5wvxs650.jpg "width=" 244 "height=" 126 "/>

Learn to use the view of Help files and learn basic commands by helping commands