Help Features in Linux

1.man

Man->>manual man is manual abbreviation
Man mans help to view man commands
Man passwd Help for viewing passwd commands

The level of man
1 system commands
2 System interface
3 Function libraries
4 special files, such as device files
5 files
6 games
7 Package for the system
8 System Administration Commands
9 cores

Man 5 passwd Help viewing the/etc/passwd file
Man 1 passwd See Help for passwd command, 1 can omit

A shortcut to the man page
Up or down a row of keys
Pageup|pagedown down a screen or to the previous screen
D|u or up half the screen
G|gg jump page to man's bottom or top
/keyword search keywords, keywords will be highlighted, n to match, n up
Q Exit help page

Usage:

Man command

Man file

2.Whatis

The Whatis command finds commands, system calls, library functions, or special file names that are specified by the command parameter in a database created with the CATMAN-W command. Whatis is searching for the keyword, the whatis command displays the header line of the manual section. You can then issue the man command to get additional information. The Whatis command is equivalent to using the MAN-F command.

Usage:

Whatis command

3.--help

The help command is used to display helper information for the shell's internal commands. The help command can only display command assistance information inside the shell. The Help information for external commands can only be viewed using the man command or the info command. Internal commands are invisible in the directory list, and they are provided by the shell itself. Common internal commands are: CD, PWD, Echo, eval, exec, export, ReadOnly, read, SHIFT, wait, and point (.).

Usage:

Command--help

Help Features in Linux