RaptorRex has asked for the wisdom of the Perl Monks concerning the following question:

It was really hard thinking of a title for this. Here is my problem:

re: CGI, I am using inline::java to create an HTML file. After the HTML file created I want to direct the browser to it. Original code was like this (pseudoy): 

java->make_HTML_file
print "location: http:.....thefileitjustmade.html\n\n";

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The problem is that the java class is printing to the output first (to the browser) thereby negating the redirection. I have no control over the insides of the java class so I have to accept this output.

I tried open(STDOUT,">/dev/null") but that didn't stop the output. The output, btw, is just a string of dots to indicate progress (this is meant to run on a command line).

I have it working now, but then comes my question.

I moved the redirection header high high above the class call in the code. Now the redirection is sent to the browser very early, long before the html file is made.

My worry is, that since the redirection is to the html file that the java is creating, that the browser will go to the file before it is finished being made.

So my questions is: what signals to a browser to proceed onto the new location? is it as soon as it receives the redirection line? or is it not until after the script completes? it does seem to work, but I want to know definitively.

Thank you.

Replies are listed 'Best First'.
Re: Does a browser execute a redirect before the script ends?
by shmem (Chancellor) on Jun 06, 2007 at 13:46 UTC
    You yould use META tags instead of outputting a 302 redirect header: 
    my $secs = 5;
my $url = 'http://foo.com/bar.html';
print qq{<meta http-equiv="refresh" content="$secs"; url=$url">\n};

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    to redirect to the new page after 5 seconds.

    Refining that, you could stuff the Java output (if it really consists of dots only) into a META tag itself: 

    print qq{<meta http-equiv="keywords" content="};
java->make_HTML_file;
print qq{">\n<meta http-equiv="refresh" content="0; url=$url"></head>\
+n};

    [download]

    (untested). That way the browser waits 'til the Java IO.OutputStream or such is finished, then reads your redirect meta directive and off it goes to the new page...

    As for redirection, re-opening STDOUT to /dev/null should work, but you might need to save your STDOUT and redirect even before the Inline::Java module is loaded, since it could get hold of a duped STDOUT, e.g. 

    #!/usr/bin/perl
package Foo;
open MYOUT, ">&STDOUT" or die "Can't dup STDOUT: $!\n";
sub say { print MYOUT "@_\n"}
package main;
open STDOUT, '>', "/dev/null" or die "open: $!\n";
print "nope";
Foo->say("oops");
__END__
Foo oops

    [download]

    - dunno, never played with that beast.

    update: added STDOUT dup example

    --shmem 

    _($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}
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