=head1 NAME
-perlfaq9 - Networking ($Revision: 1.4 $, $Date: 2001/10/31 23:54:56 $)
+perlfaq9 - Networking ($Revision: 1.15 $, $Date: 2003/01/31 17:36:57 $)
=head1 DESCRIPTION
(Alan Flavell <flavell+www@a5.ph.gla.ac.uk> answers...)
-The Common Gateway Interface (CGI) specifies a software interface between
-a program ("CGI script") and a web server (HTTPD). It is not specific
-to Perl, and has its own FAQs and tutorials, and usenet group,
-comp.infosystems.www.authoring.cgi
+The Common Gateway Interface (CGI) specifies a software interface between
+a program ("CGI script") and a web server (HTTPD). It is not specific
+to Perl, and has its own FAQs and tutorials, and usenet group,
+comp.infosystems.www.authoring.cgi
-The original CGI specification is at: http://hoohoo.ncsa.uiuc.edu/cgi/
+The original CGI specification is at: http://hoohoo.ncsa.uiuc.edu/cgi/
-Current best-practice RFC draft at: http://CGI-Spec.Golux.Com/
+Current best-practice RFC draft at: http://CGI-Spec.Golux.Com/
Other relevant documentation listed in: http://www.perl.org/CGI_MetaFAQ.html
-These Perl FAQs very selectively cover some CGI issues. However, Perl
+These Perl FAQs very selectively cover some CGI issues. However, Perl
programmers are strongly advised to use the CGI.pm module, to take care
-of the details for them.
+of the details for them.
The similarity between CGI response headers (defined in the CGI
specification) and HTTP response headers (defined in the HTTP
=head2 My CGI script runs from the command line but not the browser. (500 Server Error)
-If you can demonstrate that you've read the FAQs and that
+Several things could be wrong. You can go through the "Troubleshooting
+Perl CGI scripts" guide at
+
+ http://www.perl.org/troubleshooting_CGI.html
+
+If, after that, you can demonstrate that you've read the FAQs and that
your problem isn't something simple that can be easily answered, you'll
probably receive a courteous and useful reply to your question if you
post it on comp.infosystems.www.authoring.cgi (if it's something to do
questions but are really CGI ones that are posted to comp.lang.perl.misc
are not so well received.
-The useful FAQs, related documents, and troubleshooting guides are
+The useful FAQs, related documents, and troubleshooting guides are
listed in the CGI Meta FAQ:
http://www.perl.org/CGI_MetaFAQ.html
If you want a more complete solution, see the 3-stage striphtml
program in
-http://www.perl.com/CPAN/authors/Tom_Christiansen/scripts/striphtml.gz
+http://www.cpan.org/authors/Tom_Christiansen/scripts/striphtml.gz
.
Here are some tricky cases that you should think about when picking
You can easily extract all sorts of URLs from HTML with
C<HTML::SimpleLinkExtor> which handles anchors, images, objects,
-frames, and many other tags that can contain a URL. If you need
-anything more complex, you can create your own subclass of
-C<HTML::LinkExtor> or C<HTML::Parser>. You might even use
+frames, and many other tags that can contain a URL. If you need
+anything more complex, you can create your own subclass of
+C<HTML::LinkExtor> or C<HTML::Parser>. You might even use
C<HTML::SimpleLinkExtor> as an example for something specifically
suited to your needs.
-Less complete solutions involving regular expressions can save
+You can use URI::Find to extract URLs from an arbitrary text document.
+
+Less complete solutions involving regular expressions can save
you a lot of processing time if you know that the input is simple. One
solution from Tom Christiansen runs 100 times faster than most
module based approaches but only extracts URLs from anchors where the first
-attribute is HREF and there are no other attributes.
+attribute is HREF and there are no other attributes.
#!/usr/bin/perl -n00
# qxurl - tchrist@perl.com
=head2 How do I download a file from the user's machine? How do I open a file on another machine?
-In the context of an HTML form, you can use what's known as
-B<multipart/form-data> encoding. The CGI.pm module (available from
-CPAN) supports this in the start_multipart_form() method, which isn't
-the same as the startform() method.
+In this case, download means to use the file upload feature of HTML
+forms. You allow the web surfer to specify a file to send to your web
+server. To you it looks like a download, and to the user it looks
+like an upload. No matter what you call it, you do it with what's
+known as B<multipart/form-data> encoding. The CGI.pm module (which
+comes with Perl as part of the Standard Library) supports this in the
+start_multipart_form() method, which isn't the same as the startform()
+method.
+
+See the section in the CGI.pm documentation on file uploads for code
+examples and details.
=head2 How do I make a pop-up menu in HTML?
The best source of detailed information on URI encoding is RFC 2396.
Basically, the following substitutions do it:
- s/([^\w()'*~!.-])/sprintf '%%%02x', $1/eg; # encode
+ s/([^\w()'*~!.-])/sprintf '%%%02x', ord $1/eg; # encode
s/%([A-Fa-f\d]{2})/chr hex $1/eg; # decode
use CGI qw/:standard/;
- my $url = 'http://www.perl.com/CPAN/';
+ my $url = 'http://www.cpan.org/';
print redirect($url);
print redirect($url);
-But if coded directly, it could be as follows (the final "\n" is
+But if coded directly, it could be as follows (the final "\n" is
shown separately, for clarity), using either a complete URL or
-an absolute URLpath.
+an absolute URLpath.
print "Location: $url\n"; # CGI response header
print "\n"; # end of headers
=head2 How do I put a password on my web pages?
-That depends. You'll need to read the documentation for your web
-server, or perhaps check some of the other FAQs referenced above.
+To enable authentication for your web server, you need to configure
+your web server. The configuration is different for different sorts
+of web servers---apache does it differently from iPlanet which does
+it differently from IIS. Check your web server documentation for
+the details for your particular server.
=head2 How do I edit my .htpasswd and .htgroup files with Perl?
RFC-822 (the mail header standard) compliant, and addresses that aren't
deliverable which are compliant.
+You can use the Email::Valid or RFC::RFC822::Address which check
+the format of the address, although they cannot actually tell you
+if it is a deliverable address (i.e. that mail to the address
+will not bounce). Modules like Mail::CheckUser and Mail::EXPN
+try to interact with the domain name system or particular
+mail servers to learn even more, but their methods do not
+work everywhere---especially for security conscious administrators.
+
Many are tempted to try to eliminate many frequently-invalid
mail addresses with a simple regex, such as
C</^[\w.-]+\@(?:[\w-]+\.)+\w+$/>. It's a very bad idea. However,
this also throws out many valid ones, and says nothing about
potential deliverability, so it is not suggested. Instead, see
-http://www.perl.com/CPAN/authors/Tom_Christiansen/scripts/ckaddr.gz,
+http://www.cpan.org/authors/Tom_Christiansen/scripts/ckaddr.gz ,
which actually checks against the full RFC spec (except for nested
comments), looks for addresses you may not wish to accept mail to
(say, Bill Clinton or your postmaster), and then makes sure that the
$msg->send;
-This defaults to using L<sendmail(1)> but can be customized to use
+This defaults to using L<sendmail> but can be customized to use
SMTP via L<Net::SMTP>.
=head2 How do I read mail?
While you could use the Mail::Folder module from CPAN (part of the
-MailFolder package) or the Mail::Internet module from CPAN (also part
+MailFolder package) or the Mail::Internet module from CPAN (part
of the MailTools package), often a module is overkill. Here's a
mail sorter.
#!/usr/bin/perl
- # bysub1 - simple sort by subject
+
my(@msgs, @sub);
my $msgno = -1;
$/ = ''; # paragraph reads
while (<>) {
- if (/^From/m) {
+ if (/^From /m) {
/^Subject:\s*(?:Re:\s*)*(.*)/mi;
$sub[++$msgno] = lc($1) || '';
}
=head1 AUTHOR AND COPYRIGHT
-Copyright (c) 1997-1999 Tom Christiansen and Nathan Torkington.
+Copyright (c) 1997-2002 Tom Christiansen and Nathan Torkington.
All rights reserved.
This documentation is free; you can redistribute it and/or modify it
https://perl5.git.perl.org / perl5.git / blobdiff