About the return values of functions in Shell, shell return values

About the return values of functions in Shell, shell return values
#! /Bin/sh
Sum ()
{
Echo $($1 + $2 ))
Return $($1-$2 ))
}
Sum $1 $2
C =$ (sum $1 $2)
Echo $?
Echo $ c
Run the command:./bashTest 11 1.
The running result is:
12 -- result of sum $1 $2
10 -- echo $? Because the return value is 10.
12 -- echo $ c result, the value is 12, so c will not be attached with the return value, echo $ c calls the sum function, so print 12

Our understanding of the return values in shell is biased. The return values in shell generally refer to the return values after the command is executed. Generally, if the command is executed successfully, 0 is returned. If the command fails to be executed, 1 is returned. After the command is executed, echo $? Check the return value. In this example, because the function has a return statement, the function defines a return value. You can use echo $? Check the returned value. The value of c = $ (sum $1 $2) is not equal to the value of return, which means that the shell does not define a function in C, call the return value as c = abs (I, j.
Someone said this:
Basically, it means that the function in shell does not assign the return value of the function to a variable like other languages?
For example
C = sum_test $1 $2
Echo $ c nickname: hxl time: 10:34:00 reply hxl
No .... Nickname: lkk2003rty time: 2010-06-09 11:27:00
############### The above is from the http://blog.163.com/wangfeng2500@126/blog/static/44780245201062865644141 /##################
Correct method:Function plus (){
Read-p "input number1:" number1
Read-p "input number2:" number2
# Echo $ ($ number1 + $ number2) # The two sets of parentheses mean arithmetic operations.
Echo 'expr $ number1 + $ number2'
}
Res = $ (plus)
Echo "plus result is $ res"

Use echo, call and obtain with res = $ (plus)