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How to set an environment variable in perl so that it's visible to subsequent processes?

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Contributed by Zombie anzalone on Sep 17, 2002 at 01:18 UTC
Q&A  > programs and processes


Description:

I want to set an environment variable from within the perl script so that it's visible to other subsequent processes, like what export var=xyz does in unix shells. Something like $ENV{'var'} = 'xyz' has effect only for the current process and any children it spawns.

Answer: How to set an environment variable in perl so that it's visible to subsequent processes?
contributed by jdporter

For Unix at least, the short answer is that it can't be done. This is in the Perl FAQ, by the way: I {changed directory, modified my environment} in a perl script. How come the change disappeared when I exited the script? How do I get my changes to be visible?

Answer: How to set an environment variable in perl so that it's visible to subsequent processes?
contributed by Zombie anzalone

On Windows, you can use the Win32::AdminMisc module (by Dave Roth, not on CPAN), which has a function for this, SetEnvVar:

SetEnvVar( $Name, $Value [, $Type [, $Timeout ] ] )

This will set an environment variable $Name to $Value. This function will set the variable (creating it if $Name does not exist).
The new value will be set globally so all applications will be able to use it, unlike setting $ENV{xxx} — which sets the variable for the current process and any children it spawns afterwards.
When this function is called a broadcast to all running applications is made telling them about the variable change. An application may choose to ignore the change if it was programmed to do so.
If $Timeout is specified then the broadcast announcement will be aborted if it takes longer than $Timeout seconds (some applications may be in a hung state so they can not acknowledge the broadcast). If this timeout occurs the variable will still be updated but broadcasting it's change will be aborted.
If $Type is specified it can be one of:

ENV_SYSTEM
Specifies that $Name will be a system environment variable. (default if $Type is not specified)
ENV_USER
Specifies that $Name will be a user environment variable.

This function is the equivalent to setting an environment variable in the control panel's system applet.

NOTE: Your script will not see the new value. For that you should set $ENV{xxx}.

Example:

Win32::AdminMisc::SetEnvVar( "Temp", "$ENV{HOMEDRIVE}$ENV{HOMEPATH}", +ENV_USER, 10 );

Returns:

0 if not successful
1 if successful

Win32::AdminMisc also has a DelEnvVar function for deleting environment variables.

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