Internal command and external command of LInux
Internal command: It is transferred into the memory when the system starts, and it is resident in the memory, so the execution efficiency is high.
External command: It is a software function of the system, which is read into the memory from the hard disk when the user needs it.
type: determine whether it is an internal command
help Command
| help | for internal commands |
|---|
3. Command –help/-h
| Command –help/-h | for external commands |
|---|
4. man Command
Note that the manual manual is divided into chapters; man # Command (# indicates the chapter number)
| man Command | explain |
|---|---|
| 1 | Commands available to all users |
| 2 | System kernel calls, not every command has system calls (eg: man 2 read) |
| 3 | library call |
| 4 | Special files, such as: /dev/tty1 |
| 5 | File format (syntax of command configuration file, such as: man 5 passwd) |
| 6 | game related |
| 7 | Miscellaneous |
| 8 | Administrator commands, such as: fdisk |
5. info Command
| man Command | There are hyperlinks to stabilize the document, and info is an information page, providing more detailed information such as author, version, and when it will be released. |
|---|
6. Baidu, Google, Bing...