Scope of variables in function in unix [duplicate]

Question

I am working in Ubuntu Shell, but i want it to work for UNIX also.
Here is my code:

#!/bin/bash

func()
{
    x=42
}

x=9
func
echo $x

Why is global x changed to 42 when i changed only local variable x
Is in unix different rule for variable scopes?
Is there a method how to set return value from func to global variable, which can be used later in code?

Thank you!

The answer to most basic bash questions can be found in the manual: tiswww.case.edu/php/chet/bash/bashref.html — ccarton
– ccarton, Commented Mar 18, 2017 at 11:35
Possible duplicate of Bash variable scope, Defining common variables across multiple scripts?, How to export a variable in bash, How do I define a shell script variable to have scope outside of the script, etc. — jww
– jww, Commented May 10, 2018 at 2:36

A. L. Flanagan · Accepted Answer · 2017-03-18 01:03:43Z

0

First, you're not programming Linux; you're actually writing a function for the shell program called bash. Enter info bash on the command line to get documentation for that. For any version of Unix, what happens on the command line depends on which type of shell you're running (there are many; bash is the default for most Linux systems).

Variables in a function which are not declared are global by default. As the comment stated, you can use local to mark the variable as local to the function.

answered Mar 18, 2017 at 1:03

A. L. Flanagan

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4 Comments

SevO Over a year ago

Thank you! And about that return value, is there some method? Something with similar to var=$(fun)

A. L. Flanagan Over a year ago

It's a bit odd. You can print the result and then capture the result into a variable: $ func() { local x; x="fred"; echo $x; }; $ wilma=$(func); $ echo $wilma which prints "fred"

A. L. Flanagan Over a year ago

Or, you can return an integer as an error code: $ func() { return 42 }; func; ERR=$?; echo $ERR which will print 42. (Note there has to be a newline between the return statement and the '}', which I can't include in a comment.

SevO Over a year ago

Thank you for answers :) It helped

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