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1, Whereis

Whereis [Options] FILE

The path to the relevant files, such as binaries, source code files, and man manual pages, used to locate instructions.

The Whereis command can only be used for program name searches, and only binary files (parameter-B), man description file (parameter-m), and source code file (parameter-s) are searched. If the argument is omitted, all information is returned.

2. Enable

Enable-n internal commands to disable internal commands

Enable internal commands

3, Hash

View a list of external commands that have been executed

hash-d command clears the specified commands

Hash-r Clear All

4. TTY

View Login Terminal

5, W

View the user's logon information, and view the actions that the user is performing

6, CentOS 7 shutdown:

Halt power off continuously

Poweroff shutdown and power off, equivalent to unplug power

Shutdown-h now

Init 0

7. Reset

Fixed screen display garbled or something.

8. ① command Line Extension: $ () or '

To print the output of one command to the parameters of another command

[[email protected] ~]# echo "The system name is $ (hostname)"

The system name is CENTOS7

[Email protected] ~]# echo "I am ' WhoAmI '"

I am Root

Sometimes $ () equals '

② bracket extension: {}

Print a simplified form of a repeating string

[email protected] testdir]# touch File{1,2,3,4,5}_{txt,log,doc ...}

[Email protected] testdir]# rm-f File{1,2,3,4,5}_{txt,log,doc ...}

9, Whatis:

View a brief description of the command and the chapter number of the man in which it resides

~]# whatis command or ~]# man-f command

Use Man-f, Whatis, apropos appear nothing appropriate error message.

How to resolve:

centos6.x System:

Use root to perform Makewhatis update Whatis database

centos7.x System:

Use root to perform MANDB update Whatis database

Note: The system execution for the minimized installation is not valid.

10. Command Help:

Difference inside and outside command: # type command

Use Help:

Internal command:

#help COMMAND

#man Bash

External command:

(1) # COMMAND--help

# command-h

[Email protected] ~]# date--help

Usage:date[option] ... [+FORMAT]OR:DATE[-U|--UTC|--UNIVERSAL][MMDDHHMM[[CC]YY][.SS]]

[] is optional

Caps or <> are variables

... Represents a list

X |y| Z means "x or Y or z"

-ABC means-a-b-c

(2) User manual (manual)

# Man COMMAND

(3) Information page

# info COMMAND

(4) Help documentation for the program itself

Readme

INSTALL

ChangeLog

(5) Official program document

Official site: Documentation

(6) Official documents of the release version

(7) Google

Man Chapter Number:

1: User command

2: System call

3:C Library Call

4: Equipment files and special files

5: Configuration file format

6: Game

7: Miscellaneous

8: Commands for managing classes

9:linux Kernel API

/keyword:

Searches the end of the file from the current position with the string specified by keyword as the keyword;

N: Next

N: Previous

11. Date

[[email protected] ~]# date-d " -10day" +%f date before 10 days

2016-07-16

12. Calculator BC

13. Run the original command:

/bin/ls or ' ls ' or \ls

14, command execution priority:

Alias > Internal > Hash> External

15. Empty the command history:

Delete the history file first. bash_history; Execute History-c;exit exit

~]# history-n Scene: Terminal session A is open, copy a session window to B, then execute some commands on a, history-a write to the history file, when B reads the previous record,

The record of the history file can be read by executing history-n. (Read the new record in A's history file again)

~]# history-r Scene: Terminal session A is open, copy a session window to B, then execute some commands on a, history-a write to the history file, when B reads the previous record,

The record of the history file can be read by executing history-n. (Will read all the records in A's history file again)

~]# History-s forged an order, and did not really perform

Permanent: stored in/etc/profile (global) or ~/.bash_profile (personal)

16. File directory Structure

[[email protected] etc]# tree-l 1/ View level directory

17. Check User Login Status

18. Info

Man is often used for command reference, GNU tool info is suitable for general document reference.

No parameters, list all pages

The info page is structured like a Web site

Each page is divided into "nodes"

Before link node *

info [command]

19. Screen

Function 1: Ask for help, connect the same host, screen sharing, exit exits, can be joined by multiple terminals, all execute screen-x help can, Screen-ls view background running program

Terminal A: ~] #screen-S help Terminal B: ~]# screen-x Help

Function 2: Perform screen--------->yes--------------->ctrl+a,d after stripping------------->screen-r recovery, CTRL + C termination

20, change users do not login: (graphical interface only)

Vim/etc/gdm/custom.conf

Insert between [daemon] and [security]:

Automaticloginenable=true

Automaticlogin=root

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