Linux help command : help,--help,man,info
type command : View command type(Internal Command,External Command)
eg.:
[root@levi ~]# type -a cd
cd is a shell builtin (Internal Command)
[root@levi ~]# type -a grep
grep is /bin/grep ( External Command)
1.Internal Command (Help view)
help COMMAND
2.External Command (help view)
COMMAND --help
3.Command Manual(man)
man COMMAND
whatis COMMAND : The query where the section.
Sub sections:
1. The user command (/bin, /usr/bin, /usr/local/bin)
2. System Calls
3. The library calls
4. The special file (device file)
5. File Format (syntax of the configuration file)
6. Games
7. Miscellaneous (Miscellaneoous)
8. Management Command (/sbin, /user /sbin, /usr/local/sbin)
MAN Help symbol meaning:
[] : Optional
<> : Must be given
...: Can appear multiple times
| : A multiple-choice
{} : Grouping
Scroll screen:
Turned back one screen: SPACE
Backward one screen: b
Backward row: k
Backward line: ENTER
Find:
/ KEYWORD: back
? KEYWORD: Forward
n: next
N: Previous
q: Quit
Online Documentation
info COMMAND