Functions and recursive usage in shell

In Shell scripts, functions can be used to encapsulate a piece of reusable code that can be called multiple times, thereby improving the maintainability and reusability of the script.

Functions can divide large projects into small pieces for execution, improving the readability of the code.

The definition of a function usually has the following format:

function_name() {
    # 函数体
    ...
}

Among them, function_nameis the function name, the parentheses can contain the parameter list, and the function body contains the implementation code.

zzr () {
a=1
b=2
c=$(($a+$b))
echo $c
}
zzr

The result is obviously 3

return value

Return value: return

The return range in the shell is 0-255. If it exceeds 255, it will be modulated by 256.

When a function has return, the return value is the internal execution result of the function, so the value of echo $? is also 3, which has nothing to do with right or wrong.

The function of the return value: used to determine whether subsequent code is executed normally

Function parameter passing

Internal parameter transfer

First assign the value (read -p), then call the method (ky32), and the function passes the value to the command sequence (sum calculation)

External parameters

Need to enter variables externally

scope of function variables

sh f.sh

9 9 of global variables

8 Internal variables do not change

10 let i++

Listen to internal commands without local 9 8 8

There are local variables that need to be listened to globally.

(b is a global change and will not be affected)

function recursion

The essence is to use yourself

pow () {
        if [ $a -ne 0 ]
        then
       let sum=sum*b
       a=$(($a-1))
        pow $a $b

        fi
}
sum=1
read -p "输入指数：" a
read -p "输入底数：" b
pow $a $b
echo "$sum"

Calculate factorial

zzr () {
if [ $1 -eq 1 ]
then
echo 1
else
 local temp=$(($1-1))
 local result=$(zzr $temp)
 echo "$(($1*$result))"
fi
}
read -p "输入一个数" a
result=`zzr $a`
echo $result