Cookie question

[mstuder]

I am trying to set a cookie in the middle of my web page. Here is a testcase showing a problem that I believe is happening to me in my program. This code WORKS:

#!/usr/bin/perl -w

use strict;
use CGI qw/:standard/;
print header( 
        -type   => 'text/plain', 
        -cookie => cookie( -name=>'ident', -value=>'cookie#1')
      ); 

print "Cookie SET";

And this will NOT work:

#!/usr/bin/perl -w

use strict;
use CGI qw/:standard/;
print "Trying to set a cookie\n";
print header( 
        -type   => 'text/plain', 
        -cookie => cookie( -name=>'ident', -value=>'cookie#1')
      ); 

print "Cookie SET";

I need a way to make this work. Maybe spawn off some sort of separate process to do it? I suspect many people are having a similar problem. M

[grep]

You can do whatever you want before printing the header as just long as long as you don't print to STDOUT.

The first thing the webserver wants to see is a header, before it sends your page. If it doesn't then there is a problem. Everything sent out STDOUT goes to the webserver, so either print to STDOUT after the header or print to another file handle.
(I also recommend using the object interface of CGI)

So do this (untested):

#!/usr/bin/perl -w

use strict;
use CGI;
my $q = CGI->new();

open LOG,'>','logfile' or die "can't open logfile\n";
print LOG "Trying to set a cookie\n";

print header( 
        -type   => 'text/plain', 
        -cookie => $q->cookie( -name=>'ident', -value=>'cookie#1')
      ); 

print "Cookie SET";

OR

#!/usr/bin/perl -w

use strict;
use CGI;
my $q = CGI->new();

my $bar = do_my_cookie_stuff( $q->param('foo') );

print header( 
        -type   => 'text/plain', 
        -cookie => $q->cookie( -name=>'ident', -value=>$bar )
      ); 

print "Cookie SET";

[Fletch]

Cookies are set in the headers which have to be sent to the web browser before anything else, so of course that doesn't work.

Scent of an XY Problem aside, consider rearranging the order you do things in your code. Do all your computation / frobnication / examination of inputs first, then send whatever reply you're going to send (including the conditional cookie) at the end.

[Cubes]

If, for some reason, you absolutely have to send part of your HTML output before setting the cookie, you can put some javascript later in the page that sets a cookie on the fly.

This may come with its own set of problems, though, so rearranging things to put all of your output at the end probably is a better solution.