If you're using the object-oriented version of CGI.pm, you can set $CGI::HEADERS_ONCE++ before instantiating the CGI object to suppress multiple headers. Then, just print headers with impunity (with the caveat that if you are passing cookies or redirect headers or other things like that which could conceivably change user's session, you'll lose them if they're not printed in the first header). This may work with the function oriented version, but I haven't tested it.

The only way I know of to actually find out if the header has been printed to to examine the CGI object itself. 

$ perl -MData::Dumper -e "use CGI; my $q = CGI->new;print $q->header; 
+print Dumper($q)"
Content-Type: text/html; charset=ISO-8859-1

$VAR1 = bless( {
                 '.header_printed' => '1',
                 '.charset' => 'ISO-8859-1',
                 '.parameters' => [],
                 '.fieldnames' => {}
               }, 'CGI' );

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As you can see, the object tracks if the header has been printed, but that's not a good thing to rely on as you shouldn't be messing with the internals. The following will test for a printed header: 
use CGI;
my $q = new CGI;

# do a whole bunch of stuff

print "header printed!" if exists $q->{'.header_printed'};

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Again, that will work, but I don't recommend it. If anyone knows if CGI has a direct method for accessing that information, chime in!

Cheers,
Ovid

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In reply to (Ovid) Re: Did I already print a header? by Ovid
in thread Did I already print a header? by jptxs

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