The Shell function

Table of Contents

First, the definition of the function

function return value

Principles of use

Second, function call

---

First, the definition of the function

1.
function function name{
command
} canonical usage

2.
function name() {      The most common, the most concise
comnand
}

After the function is defined, it will not be executed automatically. It needs to be called. The advantage is that you can write a piece of function code as a function, and you can directly call it if you need it.error

function return value

return means to exit the function and return an exit value, which can be displayed by the $? variable in the script

Principles of use

1. The return value is taken as soon as the function ends, because the $? variable only returns the exit status code of the last command executed
2. The exit status code must be 0~255, and the value will be the remainder if it exceeds256

two, function call

The function can be called by writing the function name directly after the code block of the function definition in the script
#!/bin/bash
function fun1 {             defines a function called fun1
echo "this is a function!" The function of the function body is to print "this is a function!
}

fun1 , , , , , , , , writing the function name directly will run the code in the function body

Note: 1. The function name must be unique. If one is defined first, and then defined with the same name, the second one will overwrite the first function, resulting in unexpected results, so be careful not to duplicate the name here!

2. You must define a function before calling it!