Re: CGI: Waiting for Output

[benn]

Another way may be to use a redirected 'holding pattern' script that checks a semaphore set by your main program. You could even show updates - number of files processed etc.

If your main script creates a temp file that it periodically writes a status to, and deleted when finished, it could pass this filename to "holding.cgi", which can then periodically display the status, then the results when finished - something like this...

#Main File
use File::Temp;
my ($fh, $filename) = tempfile( DIR => '/tmp');
my ($hfh, $results) = tempfile( DIR => '/html');
print redirect("holding.cgi?file=$filename&html=$results");
do {
   # process record
   print $fh $num_records,"\n" unless ($num_processed++ % 1000);
} while($records_not_processed);
# write results to $hfh
# ...or just results.htm...
# ...if you haven't got multiple users / datasets etc.
unlink $filename;

#Holding.cgi
my $filename=param('file');
my $html=param('html');
if (-e $filename) {
  open FILE $filename;
  # read in last number
  # print some HTML...
  # ...that's got a META refresh in...
  # ...that points back to ourself
  close FILE;
}
else {print redirect($html);}

Cheers, Ben.

[sutch]

This works, but is a problem for sites that attempt to provide accessible content. A META refresh may disorient users, since the content may change during mid-viewing without any user interaction. Check out the W3C's Core Techniques for Web Content Accessibility Guidelines for more information.