Linux get command Help (Learn note five)

first, get order help 1.1. Internal command and external command

Simply put, the command that has a storage location in a Linux system is an external command;

There is no storage location for internal commands, which can be understood as internal commands embedded in the Linux shell, so it is not visible.

Type to determine whether an internal or internal command

[[Email protected] ~]# type help    //View the help command inside and outside the type help is a shell builtin        //You can see it as internal command [[email protected] ~]# Typ e passwd    //view passwd Whether this command exists in the Linux system passwd is/usr/bin/passwd          //Can see the storage location of passwd, and therefore exists as an external command [[email] Protected] ~]# Type cd        CD is a shell builtin   //Then passwd is an external command, then the CD is internal command

Ii. ways to get help 2.1. Help command

Help documentation for internal commands. Use the Help command word to

[[email protected] documents]# Help CD

2.2. "--help" option

Most external commands can use--help to get help, and if the command does not have the--HELP option, a simple command-format command word is displayed--help

Date--help     //Date Help

2.3. Man command

To display online Help in full screen, press Q to exit, on, down key move format: Man command word

1. Input? Keys, looking forward, such as-H, will search for rows containing "-H"
2. -Input/Key, backward lookup, such as/-k, will search backwards for "-K" rows
3. Press N or N (next) to view the previous next related match.

4. The location of the man manual can be viewed with the Manpath command to see the location of the Manpage

[email protected] documents]# manpath manpage/usr/local/share/man:/usr/share/man/ Overrides:/usr/share/man/en:/usr/share/Mans

5.man Manual Page entry

1 user instruction   2 system       3 Program Library   4 device   5  file system 6 Game       7 Miscellaneous       8 System instruction       9  kernel directives are typically used for:1,5,8

6. When using man to view the help document for a command, you can view the command's entry in the man Help document by Whatis, a command may have multiple man manual page entries (note: If the Linux computer is powered on for 70 minutes when using Whatis, Then you can use it yourself, if the Linux computer has just started, then you need to execute the makewhatis command to compile, otherwise you cannot use the Whatis command)

RM RM                   (1p)  -Remove Directory ENTRIESRM                   (1)  -  Remove files or directoriespasswdpasswd               (1 )  -Update user ' s authentication tokenspasswd               (5)  -Password filepasswd [sslpasswd]   (1SSL)  -  Compute password hashes

When querying RM or passwd commands with man, you can enter:

Mans 5 passwd        // to query the passwd Help document for the file system at the portal Mans 1 passwd        // To query passwd's help document for user instructions at the portal Mans 1 RM  

You can also write directly

Mans RM                 // Common wording Mans passwd            

2.4. Info command

Another online help, similar to the man function, is added in detail and has a relay function between different topics

Format: info command Word press Q to exit

Info RM     // RM for more information Info passwd    // to view the details of a command

General use Help,--, enough man to supplement, info with very little

Linux get command Help (Learn note five)