Re: bug attached

[Andreas Kusalananda Kähäri]

On Wed, Aug 30, 2023 at 03:40:21PM +0300, queency3 jones wrote:
> 

> From: queency3@gmail.com
> To: bug-bash@gnu.org
> Subject: 2 same var name in different function causing mix
> 
> Configuration Information [Automatically generated, do not change]:
> Machine: x86_64
> OS: linux-gnu
> Compiler: gcc
> Compilation CFLAGS: -g -O2 -fdebug-prefix-map=/build/bash-2bxm7h/bash-5.0=. 
> -fstack-protector-strong -Wformat -Werror=format-security -Wall 
> -Wno-parentheses -Wno-format-security
> uname output: Linux debian 4.19.0-25-amd64 #1 SMP Debian 4.19.289-2 
> (2023-08-08) x86_64 GNU/Linux
> Machine Type: x86_64-pc-linux-gnu
> 
> Bash Version: 5.0
> Patch Level: 3
> Release Status: release
> 
> Description:
> 
> function sub { aa=8;return_value=$aa; }
> function sub { aa=8; }
> 
> function main { aa=3;sub;aa=$(($aa+1));printf "$aa\n"; }
> 
> 
> calling main will print 9 instead of 4
> 
> 

Not a bug.

The code outputs "9" because the scope of the variable "aa" is global
(once it has been created in "main").  The second function "sub" will
therefore modify the value of the variable "aa" in the global scope.
The change in the variabel's value will be visible in "main" after the
call to "sub".

To make the variable local to the "sub" function, use the "local"
keyword:

        function sub { local aa=8; }

This will create a local variable "aa" in the function "sub" that will
not be visible outside of the function.  In particular, it will not
overwrite the global variable "aa" in "main" and the value of "aa" in
"main" will remain unchanged (until you increment it from "3" to "4").

On an unrelated note, you sohuld be printing the value using a static
formatting string, like so:

        printf '%s\n' "$aa"

This avoids interpreting the value of the variable as a printf formatting
string.

-- 
Andreas (Kusalananda) Kähäri
SciLifeLab, NBIS, ICM
Uppsala University, Sweden

.