help with perl

[Craig Sanders <cas@taz.net.au>]

I'm modifying my squid redirection script to use a database...I'd prefer
not to have to restart squid every time i update the redirections list.
The non-database version (i.e. hardcoded perl S&R statements) works
perfectly. The db version fails on some patterns.

here's a summary of what the script is supposed to do:

    given a URL, and a database of pattern & replacement key/value pairs
    check if any of the search patterns in the db can apply to it. if
    one can, then apply the pattern replacement and print the result,
    othewise print a blank line.

The database is a .db file created with 'makemap hash redir <redir' from
[:space:]-delimited source input like the following:

---cut here---
//.*excite.com/img/ads/.*			//www.taz.net.au/blank_ad.gif
//.*four11.com/g/ads/.*				//www.taz.net.au/blank_ad.gif
//.*zdnet.com/adverts/.*			//www.taz.net.au/blank_ad.gif
//.*yahoo.com/adv/.*				//www.taz.net.au/blank_ad.gif
//.*doubleclick.net/ad/.*			//www.taz.net.au/blank_ad.gif
//.*riddler.com/Commonwealth/bin/statdeploy.*	//www.taz.net.au/blank_ad.gif
---cut here---

the main use i have for squid redirections here at home is to block out
irritating flashing banner advertisements :-). i have different uses for
it at other sites which is why i want this script to be fairly generic

My script works fine with URLs containing all of the above patterns, EXCEPT
for "//.*riddler.com/Commonwealth/bin/statdeploy.*".  At first I suspected
that i may have run into some size limitation in the db key but according to
both the documentation and other test scripts i have written that is not the
case.  One of the test scripts just dumps the database in the same format as
the search & replace statements in my working non-db version.  except for
sort order, the output is identical to what's in my script.

In other words, it's almost certainly got nothing to do with perl's
database functions...it's something wrong with my comparison:
	if (($url =~ /$key/))



Here's a test of the script. I've edited it slightly to put '***' in
front of what I typed.

$ squid.redir.db
***http://doubleclick.net/ad/12345.gif 203.16.167.2 - GET
http://doubleclick.net/ad/12345.gif==>http://www.taz.net.au/blank_ad.gif
***http://www.netscape.com.au/inserts/images/advert.gif 203.16.167.2 - GET
http://www.netscape.com.au/inserts/images/advert.gif==>http://www.taz.net.au/blank_ad.gif

		These two worked fine.

***http://riddler.com/Commonwealth/bin/statdeploy?12345.gif 203.16.167.2 - GET
http://riddler.com/Commonwealth/bin/statdeploy?12345.gif==>

		For some reason, this one didn't, i got blank line output
		instead of the rewritten url.



here's what my squid.redir script currently looks like (it's gone through
several changes):

---cut here---
#!/usr/bin/perl

$debug=1 ;

use DB_File;
use Fcntl;

$|=1;

$redir_file = 'redir.db' ;

tie (%redir_db, 'DB_File', $redir_file, O_RDONLY, 0644, $DB_HASH) || die ("Cannot open $redir_file");

while (<>) {

	chop ;
	# Squid gives us: URL ip-address/fqdn ident method
	($url, $address, $ident, $method) = /(\S+)\s+(\S+)\s+(\S+)\s+(\S+)/ ;

	$out="" ;
	$found = 0 ; 

	while ((($key,$record) = each %redir_db) && ! $found) {
		if (($url =~ /$key/)) { 
			$out = $url ; 
			$out =~ s/$key/$record/ ; 
			$found = 1 ;
		 } ;
	} ;

	if ($debug) {
		print $url, "==>" ;
	} ;
	print $out, "\n" ;

}

untie %redir_db
---cut here---

I'm tempted to just give up and write it in C, but one of the purposes
of doing this is to improve my perl.

Any clues/suggestions/whatever would be appreciated.  I need to get it
working first, and optimise it for speed after that. 

thanks,

craig

--
craig sanders
networking consultant                  Available for casual or contract
temporary autonomous zone              system administration tasks.


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