Differences and basic operations of shell/sh/bash

shell/sh/bash The difference and connection

shell

shell yes “ Provide the user with the operation interface ” Software for （command interpreter, Command parser ）, It also refers to the programming language used in the command parser .
shell The role of ： User input instructions , adopt Shell Communicate with the kernel , The control hardware works normally

sh

shell Include There are many kinds of , The most commonly used are Bourne shell (sh), C shell (csh), and Korn shell (ksh).
Bourne shell (sh) yes UNIX Originally used shell , In every UNIX You can use .Bourne shell stay shell Very good at programming , But it is not as good as others in dealing with the interaction with users shell.

bash

Bourne Again shell (bash) yes sh An extension of , stay Bourne shell On the basis of the addition and enhancement of many features .bash It also includes a lot of C and Korn shell Advantages in .bash It has a very flexible and powerful programming interface , At the same time, it has a very friendly user interface .
Bourne shell The biggest drawback is that it handles user input . stay Bourne shell Typing commands can be cumbersome , and bash Make command input easier .
mac The terminal on the uses bash.

bash Common commands

1. cd： Enter a directory
   cd ～： Enter the user directory
   cd …： Return to the upper directory
   cd …/…/ Return to the upper directory
2. ls： Show All folders and files of this layer directory
3. Command Completion function ： Press twice in a row tab key , Show all commands that begin with some letters ; Press once tab key , Select the command that begins with the letter in the order of all commands .
4. ./FileName： Read and execute FileName The command
   Such as running script files （ The first line of the file must be ：#!/bin/sh）：
   Entry directory →./start.sh（ If you are prompted that permission is denied ：chmod 764 start.sh→./start.sh）
5. source FileName： It is usually used to execute the newly modified initialization document
6. vi/vim： Edit the file
   i： Enter insertion mode ;esc： Enter command mode ;
   English colon +wq： Save and exit ; English colon +q!： Do not save and exit
7. echo： Output
8. export： Display or set environment variables
   Set the environment variable ：vim ~./bashrc(or other files)→export path="/your path:$PATH"→source ~/.bashrc(or other files)
9. Variable assignment ：SPARK_STABLE=/opt/tiger/spark_deploy/spark-stable, No declaration required
   Variable usage ：${SPARK_STABLE}/bin/spark-submit
10. REPO_ROOT： General set to pwd（ root directory ）,PYTHONPATH： Directory of imported packages , Add the package directory after the default value
11. ctrl+c： Closing order , return Input status
12. mkdir file： newly build Folder ;rm file： Delete file
13. Compress and decompress ： decompression ：tar -xf file name . Extension
14. ssh： Used to encrypt when the client logs in to the server , It can also authenticate and authorize the operator .
    logon server ：ssh hostname→ Enter the password of the account → Sign in