First knowledge of SHELL commands

1, shell command commonly known as "shell", it provides a user interface with the kernel to interact with, he accepts the user input command and sends it to the kernel to execute '

The shell is actually a command interpreter that interprets the commands entered by the user and transmits it to the system kernel for execution.

The shell has its own programming language for editing the command, which allows the user to write a program composed of shell commands, and the shell becomes a language with many features of a common programming language, such as a broken structure and a branching control structure, Shell programs written in this programming language have the same effect as other applications

Explain by Process:

User input command--"Submit command to Shell (internal command and external command)--"

If it is-----------internal command--system kernel function call

If it is-----------External command or program--"Find the command file in the system and call into memory run execution--" system kernel function calls

Internal command: When the system is booted into memory, it is resident memory, so the execution efficiency is high.

External command: Is the function of the system software, the user needs to read into the memory from the hard disk

2, how to know when internal or external command?

Using the Type command, syntax: Type the command to detect

3. What can the shell command do?

For example:

Manage files (Create, delete, copy, modify)

1, the user's management (add, delete)

2, the management of related rights (authorized users of the relevant documents management, such as adding and deleting)

3, the management of the disk (partition, RAID, LVM)

4, the management of software

5, the management of the network

4. The difference between Shell "#" "$", #表示root用户, $ denotes ordinary user (need perfect Note)

Su-(account name) can switch to normal user

　　　　

First knowledge of SHELL commands