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This article mainly introduces the common Shell script test questions, the article is very detailed, has a certain reference value, interested friends must read it!

1. What is a Shell script and is it necessary?

A: an Shell script is a text file that contains one or more commands. As system administrators, we often need to use multiple commands to complete a task, and we can add all these commands in a text file (Shell script) to complete these daily tasks.

2. What types of variables can be used in Shell scripts?

Answer: in Shell scripts, we can use two types of variables: 1) system-defined variables. System variables are created by the system itself. These variables are usually made up of uppercase letters and can be viewed with the "set" command. 2) user-defined variables. User variables are generated and defined by the system user, and their values can be viewed with the command "echo $".

3. "$?" in Shell script What is the purpose of marking?

When writing a Shell script, if you want to check whether the previous command was executed successfully, use "$?" in the if condition. You can check the end status of the previous command. If the end state is 0, the previous command was executed successfully, and if the end state is not 0, the command execution failed.

4. What is the difference between the break command and the continue command in the Shell script?

A: a simple use of the break command is to exit the loop in execution. We can jump out of the loop using the break command in the while and until loops. Unlike the break command, the continue command only jumps out of the iteration of the current loop, not the entire loop. The continue command is useful in many cases, such as when an error occurs, but we still want to continue to execute the big loop.

5. How to perform arithmetic operations?

Answer: there are two ways to perform arithmetic operations: 1) use the expr command: # expr 5 + 2 + 2) use a dollar sign and square brackets ($[expression]) for example: test=$ [16 + 4]; test=$ [16 + 4]

6. What is the use of each loop in the Shell script?

1) the basic syntax of for loop:

For variable in Loop list

Do

Command 1

Command 2

... .

Final order

Done

2) the while loop repeats its command block as long as the condition is established. Unlike the for loop, the while loop iterates until its condition is not true. Basic grammar:

While [condition]

Do

Command...

Done

3) the basic format of do-while statements?

A: the do-while statement is similar to the while statement, but executes the command before checking the conditional statement (LCTT translation means at least once). The syntax of the do-while statement:

Do

{

Command

} while (condition)

These are all the contents of this article entitled "what are the common Shell script questions?" Thank you for reading! Hope to share the content to help you, more related knowledge, welcome to follow the industry information channel!

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