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List:       perl-win32-users
Subject:    Re: Perl for ISAPI
From:       John Deurbrouck <john () pcpix ! com>
Date:       2002-06-28 18:36:58
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I tried to optimize by doing this:

#prime the %ENV pump with all actual environment variables
my @env_vars = (`envdump.exe` =~ /(.+?)=.*\n/g);
for (@env_vars) { if (exists($ENV{"$_"})) { } }

Unfortunately it doesn't work, because the child process isn't created with 
a new copy of the parent environment, but rather the %ENV data. Thus you 
end up with the same list in %ENV you had at the beginning.

Here's the code I ended up with, which makes the effort to delete strings 
that don't exist in the environment.

#prime the %ENV pump
{
         @env_vars = qw (
                       # this should be the list of env vars you're 
interested in, perhaps generated by the tool from the previous post
                       # abbreviated to conserve bandwidth
                 HTTP_ACCEPT
                 HTTP_ACCEPT_LANGUAGE
                 HTTP_CONNECTION
                 HTTP_HOST
                 HTTP_REFERER
                 HTTP_USER_AGENT
                 HTTP_ACCEPT_ENCODING
                 QUERY_STRING
                 REMOTE_ADDR
                 REMOTE_HOST
                 REQUEST_METHOD
         );
         for (@env_vars) {
           if (exists($ENV{$_})) {
             if (!defined$ENV{$_} or length($ENV{$_})<1) { delete $ENV{$_} }
           }
         }
}


--- John

>That is, for every environment variable my C++ program reported, I wanted 
>Perl to grab the external data if possible. I discovered I didn't need to 
>actually assign anything. I could just do an exists test. Thus, for every 
>known possible environment variable, I had a line like the following in my 
>Perl script:
>
>if (exists($ENV{'HTTP_ACCEPT'})) { $countem++ }
>if (exists($ENV{'HTTP_ACCEPT_LANGUAGE'})) { $countem++ }
>
>Not elegant of course. A qw() creating an array, then a for (@arr) {} 
>would have been cleaner. Editor macros sometimes lead to brain laziness. 
>Anyway...
>
>Now I can see that ALL the stuff I needed is available. And I can stop 
>downloading this huge IIS manual I was getting off the Microsoft site.

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