Linux get help information for commands

Hello everyone, I am ZYJTF lonely cloud Twilight Rain, long time no blog, today brought to you is " how to get the use of Linux commands help information "

Query Internal command : Help command...
?? Help is an internal command that outputs all of the shell's internal commands and the use of the shell's internal commands.
?? Use Syntax :
???? output shell-All internal commands : Help
???? Output Shell Internal command usage help information :
???????????????????? Help Options COMMAND ...
????? # Command: internal command to query
????? # ... meaning can occur multiple times
Command Options :
??? -D: A short description of the output command
??? -M: Display as a pseudo-MAM manual

Querying external commands
? 1. COMMAND? {--help|-h}
??? This method is defined by the source code in the command and can be used to output a brief description of the command

? 2. Use the Man (manual) manual to query for external commands
??? The man command is an external command for querying command Help information on the system, how to use the configuration file, and information such as device file special files and system call library calls.
??? syntax : Man to query the content ...
?????? Man serial number to query the command or configuration file ...
?????? Man serial number option to query the content ...
?????? Man serial number KEYWORD
??? Options :
?????? -A: Search in all man help manuals
?????? -K Word: Lists the man pages that are related to the specified WORD
?????? -F: Equivalent to the Whatis command, which displays a short description of the given keyword
?????? -m/path/to/somedir: Specifies the path of the search for the man manual
???? corresponding serial number (chapter)
????? Use the man manual (compressed file) There are chapters, different chapters can query the content is not the same, not a command in all chapters have content

??? 1: General user commands
??? 2: Functions and tools called by the kernel
??? 3: Common Function-domain libraries (C-Library calls)
??? 4: Equipment files and special files
??? 5: Configuration file
??? 6: Game Use Help
??? 7: Formula and Agreement (miscellaneous)
??? 8: Management tools and Daemons
??? 9: kernel-related files

???? Use the Whatis command to query the command function (which section is helpful)
???? syntax : Whatis COMMAND
???? This command executes the process of querying the database and manually updating the database: Makewhatis

? ?? Export the man manual page content to a file
???? syntax : Man COMMAND | Col-b > FILENAME

??? Note: When using man to query configuration files or other files, do not write absolute path, write on the name to query

?? Man manual page paragraph description (section)

• ? NAME: Brief description of functionality
• ? Synopsis: Syntax format
• ? DESCRIPTION: Detailed description of function
• ? options: Option
• ? EXAMPLES: Using the example
• ? AUTHOR: Author
• ? BUGS: How to Report program bugs
• ? REPORTING BUGS: Contact to report a bug
• ? See ALSO: Additional references

??? Synopsis option (symbol in man manual) description

• ? []: Optional content
• <>: What you must provide
• ? {}: Grouping, there are more than one content in general
  ?? A|b|c: Choose one More
• ?... : Similar content can appear multiple

Man manual page shortcut keys Shortcut key	description
Ctrl+d key, CTRL + D key	Turn half screen down or turn half screen at the end of the file
Ctrl+u Key, Ctrl+u key	Flip up half screen or turn half screen to file header
Arrow keys ↓, enter, j command, E command	To flip a line or flip a line to the end of a file
Arrow key ↑,k command, y command	To turn up one line or one line to the file header
Space key, Page down key	Turn down one page or one screen at the end of a file
Page up,b Key	Turn up a page or flip a screen to the file header
End key, Command g	Go to the last page or jump to the last line
Home key, command: 1G	Go back to first page or jump to line one
: Number of rows, number of rows, g	Go to the specified line
Q,q	Exit

?? Man Text Search command
???? You can use the following command to search for text in the man manual

???? /keyword : Search from the current position to the end of the file, without distinguishing the character case
???? keyword : Search from current position to file header
?????? n: Same direction as Find command
?????? N: Opposite of Find command direction

? 3. Use the Info page to query the command
??? Info gets the online documentation for the command, supports hyperlinks
??? syntax : info COMMAND

? 4. Using Search engine query
??? Google
??? Search :Linux? filetype:pdf
????? A PDF file of Linux appears
??? Search :zyjtf Lonely Cloud Twilight site:blog.51cto.com (do not add www)
????? The "ZYJTF cloud Twilight " keyword appears in the blog.51cto.com website

? 5. Official Program Documentation
??? "Document" on the official site
???????? ? Documentation

? 6. Documentation of the program's own Help
??? Many applications will bring their own Help documentation:/usr/share/doc/app-version

??? README: Information related to the program
??? Install: Installation Help
??? Changes: Change information at version iteration

? 7. Official documentation of the mainstream distribution

• ? Rhel Official Documentation
  ?? http://redhat.com/docs
  ?? https://access.redhat.com/documentation/en/

Linux get help information for commands