linux--Help Document Acquisition

access to help documents

External command: There is an executable program , located in a file system directory, you can use which, Whereis command query to the location of the command store.

• The path of the shell program search executable file is defined in the PATH environment variable, from left to right, and using the # echo $PATH command to view.

1. Get internal command help:

Format: # Help COMMAND

A.hash command:

Command format:hash [-LR] [-P path name] [-DT] [name ...]

The path result of the external command that the shell has searched for is cached into the KV (key-value) store;

Options:

• -R Forget all places to remember

B.history command:

Function: Management command history;

When you log in to the shell, the commands that are recorded in the command history file are read: ~/.bash_history

The newly executed commands are only recorded in the cache when logged into the shell, and are "appended" to the command history file when the user exits;

Options:

• -A: Append the newly executed command history list to the history file in this session;
• -D: Deletes the command specified in the history;
• -C: Clears the command history;

Quick action:

• !#: Call the section # command in history;
• !string: Invokes the last command in history that starts with a string;
• !: previous command;

2, external command to help obtain:

Format: # man COMMAND

Manual page Location:/usr/share/man

The man command has man1~man8,8 levels of help documentation:

• Man1: User Commands
• Man2: System call
• MAN3:C Library Call
• MAN4: Equipment files and special files
• MAN5: Configuration file format
• Man6: Games
• MAN7: Miscellaneous
• MAN8: Commands for managing classes

See the Manual in Chapter #: Man# COMMAND

The paragraph description in the Help manual:

• Name: explanation of the names
• Synopsis: Usage rules
  • []: Optional content
  • <>: Required Content
  • A|b: Two Choose one
  • ...: The same content can appear multiple times
• DESCRIPTION: Description of the relevant (option) usage

How to operate the man command:

function key	function
SPACEBAR, ^v, ^f, ^f	display the next screen of the man page
enter key, ^n, E, ^e or J or ^j	one scroll man page A line of
y, ^y, ^p, K, ^k	to the header of the file
B, ^b	rollback one screen
D, ^d	turn half screen to file footer
U, ^u	turn half screen to file header
f	roll forward one screen
q	exit man command
h	list all function keys
/word	Search word string
#	jump to # line
1g	Back to file header
G	Turn to end of file

Text Search:

• /keyword: Searches the end of the file from the current position with the string specified by KEYWORD, and does not distinguish between case-insensitive characters;
• N: Next
• N: Previous
• ? KEYWORD: The string specified by the KEYWORD keyword, from the current position to the file header search;
  • N: Same direction as search command, next
  • N: Follow the search command in the opposite direction, previous

linux--Help Document Acquisition