Question

Setting environment variable via Win32::TieRegistry

Asked by: FishMonger

I'm trying to set an environment var and have it persist after the perl script ends.  Setting the ENV var via Win32::TieRegistry is easy, however, unless I logout/login that environment setting isn't available to other processes.  So, the question is: how do you reload the registry without having to logout?

For background context, this is part of a Tk login script that upon authentication, will launch a batch file via exec.  So, the final solution could be either Perl related or a windows command executed in the batch file

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Asked On
2008-04-01 at 20:05:41ID23288000
Topics

Perl Programming Language

,

Microsoft Windows Operating Systems

,

Scripting Languages

Participating Experts
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Points
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Answers

 

by: FishMongerPosted on 2008-04-01 at 20:10:47ID: 21259928

Here's my test script.

use strict;
use warnings;
use Win32::TieRegistry( Delimiter=>"/" );
 
$Registry->{"HKEY_CURRENT_USER/Environment/POS_SYS"} = "G=DEPT99 D=99 N=MGR";
 
print $Registry->{"HKEY_CURRENT_USER/Environment/POS_SYS"}, $/;
print $ENV{POS_SYS}, $/;

                                              
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by: Adam314Posted on 2008-04-01 at 20:21:08ID: 21259970

Unless you want the entire registry reloaded, you could do it in two steps: first add it to the registry as you are doing, then set $ENV{POS_SYS} = "G=DEPT99 D=99 N=MGR" for the environment in the current login.

 

by: FishMongerPosted on 2008-04-01 at 20:37:20ID: 21260021

Sorry, I guess I wasn't clear enough.  I'm not concerned with the current running process.  I need it to be persistent.  Meaning that If I open a new cmd window after running the test script, I should be able to utilize that ENV setting.

If you run the test script (with or without manually assigning $ENV{POS_SYS} and check your env via "My Computer"->Settings->Environment you'll see that the env var is set.  But if you open a cmd window and output your env settings, you'll see that it's not there unless you logout/login.

Here's the results I get after adding the ENV assignment as you suggest.

D:\POS>setenv.pl
G=DEPT99 D=99 N=MGR
G=DEPT99 D=99 N=MGR
 
D:\POS>echo %POS_SYS%
%POS_SYS%
                                              
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by: Adam314Posted on 2008-04-02 at 11:11:12ID: 21265759

No, you were clear - that was my mistake.

You can use this registry key to affect the current environment:
HKEY_LOCAL_MACHINE/SYSTEM/CurrentControlSet/Control/Session Manager/Environment/

It won't affect any already started processes, but it will affect any newly started processes.

$Registry->{"HKEY_LOCAL_MACHINE/SYSTEM/CurrentControlSet/Control/Session Manager/Environment/POS_SYS"}
  = "G=DEPT99 D=99 N=MGR";
                                              
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by: FishMongerPosted on 2008-04-02 at 14:14:38ID: 21267613

Unfortunately, that suffers from the same problem as setting it in HKEY_CURRENT_USER i.e., it still requires a logout/login to take effect.  Additionally, setting it in HKEY_LOCAL_MACHINE creates the secondary issue of being applied to all user accounts.

I've also been informed of a change in the requirements.  This environment setting needs to be applied only to the current user and should not be retained across logins/reboots.  I've found a setx command in the Windows Resource Kit that propagates the environment setting for any newly started processes without the need to logout/login, which solves the first part of the problem.  Unfortunately, the setting is retained across logins/reboots.

 

by: Adam314Posted on 2008-04-02 at 15:15:36ID: 21268101

I just tried that code again, and it didn't work - and I was sure it worked before - thought I was going crazy.

A little more testing, and I found out if I run that code, then start a new process, it does NOT have the new environment variable.  After a while, doing other things on the computer (but never logging out), I start a new process, and it DOES have the new environment variable.  So it seems that something will cause windows to re-read the registry without logging out/in.  Not sure what that is... still looking.  I have found that if i right-click my computer, select properties, select advanced tab, click environment variables (don't change anything), click OK, this always seems to cause windows to reload the environment from registry.  I didn't do that before, and the new environment variable was processed, so there must be other things that cause it also.

I'm running XP Pro, SP2.  Can you test and see if you get the same behavior?

I also found this key in the registry:
    HKEY_CURRENT_USER/Volatile Enviornment/
But setting things there does not seem to take effect, at least not with what I've been doing.

 

by: FishMongerPosted on 2008-04-02 at 16:33:20ID: 21268522

I think I found out why the setting was taking (immediate) effect and a possible solution, but I'm still testing.

http://barnyard.syr.edu/%7Evefatica/#SETENV

 

by: FishMongerPosted on 2008-04-02 at 16:34:00ID: 21268527

s/was/was not/

 

by: FishMongerPosted on 2008-04-08 at 21:59:19ID: 21311877

Adam,

I ended up using the setenv utility that I found instead of Win32::TieRegistry as I originally planned.  Even though your suggestions didn't resolve my problem, you did point me to the proper reg key (which I also came across at the same time).

Thanks

 

by: Adam314Posted on 2008-04-09 at 07:09:02ID: 21315027

Glad you got it working.

20120131-EE-VQP-002

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