X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=pod%2Fperlfaq9.pod;h=609f8984851bdb5c16f88091d9687ce846b83593;hb=b9ad30b40cf004f5ea6fd7a945a950cf873aed7b;hp=336d22d5e9b22ac9a3dbcd8ac582e6f234d47d09;hpb=b68463f7111b76264d78b38de603c7c4a3c5e635;p=p5sagit%2Fp5-mst-13.2.git

diff --git a/pod/perlfaq9.pod b/pod/perlfaq9.pod
index 336d22d..609f898 100644
--- a/pod/perlfaq9.pod
+++ b/pod/perlfaq9.pod
@@ -1,6 +1,6 @@
 =head1 NAME
 
-perlfaq9 - Networking ($Revision: 1.23 $, $Date: 2005/08/10 15:54:54 $)
+perlfaq9 - Networking ($Revision: 8539 $)
 
 =head1 DESCRIPTION
 
@@ -186,11 +186,29 @@ 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?
+=head2 How do I make an HTML pop-up menu with Perl?
+
+(contributed by brian d foy)
+
+The CGI.pm module (which comes with Perl) has functions to create
+the HTML form widgets. See the CGI.pm documentation for more
+examples.
+
+	use CGI qw/:standard/;
+	print header,
+		start_html('Favorite Animals'),
+
+		start_form,
+			"What's your favorite animal? ",
+        popup_menu(
+        	-name   => 'animal',
+			-values => [ qw( Llama Alpaca Camel Ram ) ]
+			),
+        submit,
+
+ 		end_form,
+        end_html;
 
-Use the B<< <SELECT> >> and B<< <OPTION> >> tags.  The CGI.pm
-module (available from CPAN) supports this widget, as well as many
-others, including some that it cleverly synthesizes on its own.
 
 =head2 How do I fetch an HTML file?
 
@@ -253,19 +271,18 @@ the content appropriately.
 
 =head2 How do I decode or create those %-encodings on the web?
 
-
 If you are writing a CGI script, you should be using the CGI.pm module
 that comes with perl, or some other equivalent module.  The CGI module
 automatically decodes queries for you, and provides an escape()
 function to handle encoding.
 
-
 The best source of detailed information on URI encoding is RFC 2396.
 Basically, the following substitutions do it:
 
     s/([^\w()'*~!.-])/sprintf '%%%02x', ord $1/eg;   # encode
 
-    s/%([A-Fa-f\d]{2})/chr hex $1/eg;            # decode
+    s/%([A-Fa-f\d]{2})/chr hex $1/eg;                # decode
+	s/%([[:xdigit:]]{2})/chr hex $1/eg;          # same thing
 
 However, you should only apply them to individual URI components, not
 the entire URI, otherwise you'll lose information and generally mess
@@ -312,7 +329,7 @@ an absolute URLpath.
 
 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
+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.
 
@@ -366,9 +383,9 @@ C<param()> function.
 
 	use CGI qw(:standard);
 
-	my $total = param( "price" ) + param( "shipping" );
+	my $total = param( 'price' ) + param( 'shipping' );
 
-	my @items = param( "item ); # multiple values, same field name
+	my @items = param( 'item' ); # multiple values, same field name
 
 If you want an object-oriented approach, CGI.pm can do that too.
 
@@ -376,9 +393,9 @@ If you want an object-oriented approach, CGI.pm can do that too.
 
 	my $cgi = CGI->new();
 
-	my $total = $cgi->param( "price" ) + $cgi->param( "shipping" );
+	my $total = $cgi->param( 'price' ) + $cgi->param( 'shipping' );
 
-	my @items = $cgi->param( "item" );
+	my @items = $cgi->param( 'item' );
 
 You might also try CGI::Minimal which is a lightweight version
 of the same thing.  Other CGI::* modules on CPAN might work better
@@ -390,54 +407,52 @@ of the task.  It's much easier and less hassle to use CGI.pm.
 
 =head2 How do I check a valid mail address?
 
-You can't, at least, not in real time.  Bummer, eh?
+(partly contributed by Aaron Sherman)
 
-Without sending mail to the address and seeing whether there's a human
-on the other end to answer you, you cannot determine whether a mail
-address is valid.  Even if you apply the mail header standard, you
-can have problems, because there are deliverable addresses that aren't
-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.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
-hostname given can be looked up in the DNS MX records.  It's not fast,
-but it works for what it tries to do.
+This isn't as simple a question as it sounds.  There are two parts:
 
-Our best advice for verifying a person's mail address is to have them
-enter their address twice, just as you normally do to change a password.
-This usually weeds out typos.  If both versions match, send
-mail to that address with a personal message that looks somewhat like:
+a) How do I verify that an email address is correctly formatted?
 
-    Dear someuser@host.com,
+b) How do I verify that an email address targets a valid recipient?
 
-    Please confirm the mail address you gave us Wed May  6 09:38:41
-    MDT 1998 by replying to this message.  Include the string
-    "Rumpelstiltskin" in that reply, but spelled in reverse; that is,
-    start with "Nik...".  Once this is done, your confirmed address will
-    be entered into our records.
+Without sending mail to the address and seeing whether there's a human
+on the other end to answer you, you cannot fully answer part I<b>, but
+either the C<Email::Valid> or the C<RFC::RFC822::Address> module will do
+both part I<a> and part I<b> as far as you can in real-time.
+
+If you want to just check part I<a> to see that the address is valid
+according to the mail header standard with a simple regular expression,
+you can have problems, because there are deliverable addresses that
+aren't RFC-2822 (the latest mail header standard) compliant, and
+addresses that aren't deliverable which, are compliant.  However,  the
+following will match valid RFC-2822 addresses that do not have comments,
+folding whitespace, or any other obsolete or non-essential elements.
+This I<just> matches the address itself:
+
+    my $atom       = qr{[a-zA-Z0-9_!#\$\%&'*+/=?\^`{}~|\-]+};
+    my $dot_atom   = qr{$atom(?:\.$atom)*};
+    my $quoted     = qr{"(?:\\[^\r\n]|[^\\"])*"};
+    my $local      = qr{(?:$dot_atom|$quoted)};
+    my $domain_lit = qr{\[(?:\\\S|[\x21-\x5a\x5e-\x7e])*\]};
+    my $domain     = qr{(?:$dot_atom|$domain_lit)};
+    my $addr_spec  = qr{$local\@$domain};
+
+Just match an address against C</^${addr_spec}$/> to see if it follows
+the RFC2822 specification.  However, because it is impossible to be
+sure that such a correctly formed address is actually the correct way
+to reach a particular person or even has a mailbox associated with it,
+you must be very careful about how you use this.
 
-If you get the message back and they've followed your directions,
-you can be reasonably assured that it's real.
+Our best advice for verifying a person's mail address is to have them
+enter their address twice, just as you normally do to change a
+password. This usually weeds out typos. If both versions match, send
+mail to that address with a personal message. If you get the message
+back and they've followed your directions, you can be reasonably
+assured that it's real.
 
 A related strategy that's less open to forgery is to give them a PIN
 (personal ID number).  Record the address and PIN (best that it be a
-random one) for later processing.  In the mail you send, ask them to
+random one) for later processing. In the mail you send, ask them to
 include the PIN in their reply.  But if it bounces, or the message is
 included via a "vacation" script, it'll be there anyway.  So it's
 best to ask them to mail back a slight alteration of the PIN, such as
@@ -596,29 +611,37 @@ Or more succinctly,
     $msg[$msgno] .= $_;
     END { print @msg[ sort { $sub[$a] cmp $sub[$b] || $a <=> $b } (0 .. $#msg) ] }
 
-=head2 How do I find out my hostname/domainname/IP address?
+=head2 How do I find out my hostname, domainname, or IP address?
+X<hostname, domainname, IP address, host, domain, hostfqdn, inet_ntoa,
+gethostbyname, Socket, Net::Domain, Sys::Hostname>
 
-The normal way to find your own hostname is to call the C<`hostname`>
-program.  While sometimes expedient, this has some problems, such as
-not knowing whether you've got the canonical name or not.  It's one of
-those tradeoffs of convenience versus portability.
+(contributed by brian d foy)
 
-The Sys::Hostname module (part of the standard perl distribution) will
-give you the hostname after which you can find out the IP address
-(assuming you have working DNS) with a gethostbyname() call.
+The Net::Domain module, which is part of the standard distribution starting
+in perl5.7.3, can get you the fully qualified domain name (FQDN), the host
+name, or the domain name.
 
-    use Socket;
-    use Sys::Hostname;
-    my $host = hostname();
-    my $addr = inet_ntoa(scalar gethostbyname($host || 'localhost'));
+	use Net::Domain qw(hostname hostfqdn hostdomain);
+
+	my $host = hostfqdn();
+
+The C<Sys::Hostname> module, included in the standard distribution since
+perl5.6, can also get the hostname.
+
+	use Sys::Hostname;
+
+	$host = hostname();
 
-Probably the simplest way to learn your DNS domain name is to grok
-it out of /etc/resolv.conf, at least under Unix.  Of course, this
-assumes several things about your resolv.conf configuration, including
-that it exists.
+To get the IP address, you can use the C<gethostbyname> built-in function
+to turn the name into a number. To turn that number into the dotted octet
+form (a.b.c.d) that most people expect, use the C<inet_ntoa> function
+from the <Socket> module, which also comes with perl.
 
-(We still need a good DNS domain name-learning method for non-Unix
-systems.)
+    use Socket;
+
+    my $address = inet_ntoa(
+    	scalar gethostbyname( $host || 'localhost' )
+    	);
 
 =head2 How do I fetch a news article or the active newsgroups?
 
@@ -640,9 +663,17 @@ available from CPAN) is more complex but can put as well as fetch.
 Use one of the RPC modules you can find on CPAN (
 http://search.cpan.org/search?query=RPC&mode=all ).
 
+=head1 REVISION
+
+Revision: $Revision: 8539 $
+
+Date: $Date: 2007-01-11 00:07:14 +0100 (Thu, 11 Jan 2007) $
+
+See L<perlfaq> for source control details and availability.
+
 =head1 AUTHOR AND COPYRIGHT
 
-Copyright (c) 1997-2005 Tom Christiansen, Nathan Torkington, and
+Copyright (c) 1997-2007 Tom Christiansen, Nathan Torkington, and
 other authors as noted. All rights reserved.
 
 This documentation is free; you can redistribute it and/or modify it