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函数内的“return”是强制要求吗？

tag-icon • tag-icon bash
函数内的“return”是强制要求吗？

函数的更简单形式是：

name () { commands return }

我发现有和没有 return 的函数没什么区别。
假设最小代码：

step_forward (){
    echo "step one;"
    return
}
turn_around() {
    echo "turn around."
    return
}

step_forward
turn_around

运行并检查退出状态：

$ bash testing.sh
step one;
turn around.
$ echo $?
0

注释掉之后再次运行return

$ bash testing.sh
step one;
turn around.
$ echo $?
0

在什么情况下函数应该以返回结束？

答案1

return函数中不需要值。通常在return脚本中会使用 来返回退出值。退出值通常类似于1或 ，0许多脚本编写者可能会将其用作 表示0成功和1表示不成功。

#!/bin/bash
#The following function returns a value of 0 or 1
function if_running(){
    ps -ef | grep -w "$1" | grep -v grep > /dev/null
    if [[ $? == 0 ]]; then
        return 0
    else
        return 1
    fi
}

#Read in name of a running process
read -p "Enter a name of a process: "

#Send REPLY to function
if_running $REPLY

#Check return value and echo appropriately
if [[ $? == 0 ]]; then
   echo "Return value is $?"
   echo "$REPLY is running..."
else
   echo "Return value is $?"
   echo "$REPLY is not running..."
fi

例子：

~$ ./ps_test.bsh 
Enter a name of a process: ls
Return value is 1
ls is not running...

~$ ./ps_test.bsh 
Enter a name of a process: bash
Return value is 0
bash is running...

我之前写的这个答案没有返回值，但仍然给出输出 https://askubuntu.com/a/1023493/231142

#!/bin/bash
function area(){
    circ=$(echo "3.14 * $1^2" | bc)
}

#Read in radius
read -p "Enter a radius: "

#Send REPLY to function
area $REPLY

#Print output
echo "Area of a circle is $circ"

例子：

terrance@terrance-ubuntu:~$ ./circ.bsh 
Enter a radius: 6
Area of a circle is 113.04

希望这可以帮助！

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