Control statements executed by bash scripts

1. control statements executed by bash scripts:

1. sequential execution: by default, each statement is executed one by one.

2. Select execution: Branch, condition judgment, and execution of qualified branches.

If

3. Loop execution: the same piece of code is repeatedly executed for a limited number of times.

A. For: knows the number of cycles,

For var_name in list;

Do

Loop body

Done

For example, add three users cyclically; Xiaowang, Xiaoli, and xiaosun

#! /Bin/bash

For username in Xiaowang Xiaoli xiaosun;

Do

Useradd $ username

Done

List generation method:

Generate number: {start... end}, seq [start] [STEP] End

Example: generate 10 users, which are user101. .. user110

For username in 'seq 101 110 ';

Do

Useradd user $ username

Done

For example, delete the 10 users generated above and delete the user's home directory.

For username in {101... 110 };

Do

Userdel-r user $ username

Done

B. While:

C.:

Ii. Check the bash script syntax command: Bash-N script file

3. Execute the Script: Bash script file. You do not need to modify the execution permission of the file.

Control statements executed by bash scripts