Linux Learning Notes (6) Help commands for Linux common commands and user management commands

(1) Man

The man command is used to obtain help information for a command or configuration file , the English original is manual, where the path is/usr/bin/man, and its syntax is:

Man [command or configuration file]

Note: You do not need an absolute path to view the Help information for a configuration file .

Viewing the Help for a command primarily looks at the purpose of the command (name) and the corresponding options , while the Help for the configuration file is primarily to view the storage information (name) and its corresponding format . Each configuration file in Linux has a corresponding format.

For help with the LS command, man ls, view the Help for the services configuration file under/ect: Man services.

Exception: When you view the passwd configuration document Help, the Help information for the passwd command is displayed:

Mans passwd PASSWD (1)            User Utilities               PASSWD (1) NAME       PASSWD - update user ' s authentication tokens Synopsis       passwd  [-K] [-l] [-u [-f]] [-d] [-e] [-N mindays] [-x maxdays]       [-< C16>w Warndays] [-I inactivedays] [-S] [--stdin] [username]

Then use the Whereis command to view the path to the passwd:

Whereis passwd passwd:/usr/bin/passwd /etc/passwd /usr/share/man/man1/passwd. 1. gz/usr/share/man/man5/passwd. 5. gz

You can see that passwd exists in two places, where the "1" in man1/passwd.1.gz represents the help of the command, and "5" in man5/passwd.5.gz represents the Help for the configuration file , so You can view help for a configuration file in the following ways:

Mans 5 passwd PASSWD (5)           Linux Programmer ' s Manual         PASSWD (5) NAME       PASSWDfile  DESCRIPTION       Passwd  is  a  text  file, that contains a list of the system ' s

(2) Whatis

The Whatis command provides a brief description of the command , not as fully displayed as a man, in the form of:

Man [command]

Example: Displays a short help message for LS:

ls ls                   (1)  - List Directory contentsls                   (1p)  -List Directory contents

(3) Apropos

The apropos command is used to view short information for a configuration file in the following syntax format:

Apropos [config file]

Example: Displays a short help message for inittab under/etc:

[Email protected] ~]# Apropos Inittabinittab              (5)  -init daemon configuration

(4)--help

a command plus-help to display the main options for the command , such as the main options for displaying the touch command:

Touch -Helpusage:touch  [options] ... File... Change the access time and modification time for each file to the current time. Files that do not exist will be created as empty files unless you use the-C or-h option. If the file name is "-" then special processing changes the access time of the files associated with the standard output. The long option must use parameters that are also required for short options.   -A                    only change the access  time -C,--no-       Create creates no  file -D,--Date= string     representing time instead of current time  - F                    (ignored) using the specified string

(5) Help

The help command is used to obtain a helper message for the shell's built -in command, which uses the Which,whereis command to not find the command that is located on the path , and helps is a built-in command with the syntax format:

Help [command]

Example: Find Help for Umask:

[Email protected] ~]# help Umaskumask:umask [-P] [-S] [mode]     file mode mask.

Note:help can also be used to view assistance for Shell programming if, case, while, and so on .

(6) Useradd

The useradd command is used to add a new user , where the path is/usr/sbin/useradd, with the syntax format:

useradd [user Name]

(7) passwd

The passwd command is used to set the user password , where the path is/USR/BIN/PASSWD, in the syntax format:

passwd [user Name]

Note: Passwords must conform to the password specification.

(8) Who

The who command is used to view login user information , where the path is/usr/bin/who,

W.H.O. root     tty1         --£ ºroot     pts/ 0        ------£ ºPanax notoginseng 　

The first root is the login username, the second TTY represents the local terminal, the PTS represents the remote terminal, and the last field is the logon time .

(9) W

The W command is used to view details of the logged-in user , where the path is/usr/bin/w

[Email protected] ~]#W -: to: -Up2: $,2Users, load average:0.04,0.02,0.00USER TTY from [email protected] IDLE jcpu PCPU whatroot tty1-Wed22 5days0.63s0.63s-bashroot pts/0     10.2.108.214Wed220.00s3.80s0.01sW

Where up shows the server running time , loadAverage indicates the load of the server , what indicates thecurrent user is executing the command ,JCPU indicates the cumulative CPU time, PCPU represents the CPU time that the current execution command consumes .

Linux Learning Notes (6) Help commands for Linux common commands and user management commands