X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=pod%2Fperlfaq9.pod;h=609f8984851bdb5c16f88091d9687ce846b83593;hb=42e1efa1e62f0d241a2d8e4847bce98f732060a3;hp=d1bd593dfe7690c16f2a977b086d5e302a7eb48b;hpb=f1cbbd6ecad59f8e4d9d331daa6642ebfd972ae1;p=p5sagit%2Fp5-mst-13.2.git

diff --git a/pod/perlfaq9.pod b/pod/perlfaq9.pod
index d1bd593..609f898 100644
--- a/pod/perlfaq9.pod
+++ b/pod/perlfaq9.pod
@@ -1,45 +1,70 @@
 =head1 NAME
 
-perlfaq9 - Networking ($Revision: 1.26 $, $Date: 1999/05/23 16:08:30 $)
+perlfaq9 - Networking ($Revision: 8539 $)
 
 =head1 DESCRIPTION
 
 This section deals with questions related to networking, the internet,
 and a few on the web.
 
-=head2 My CGI script runs from the command line but not the browser.   (500 Server Error)
+=head2 What is the correct form of response from a CGI script?
 
-If you can demonstrate that you've read the following 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
-with HTTP, HTML, or the CGI protocols).  Questions that appear to be Perl
-questions but are really CGI ones that are posted to comp.lang.perl.misc
-may not be so well received.
+(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 CGI specification is outlined in an informational RFC:
+http://www.ietf.org/rfc/rfc3875
+
+Other relevant documentation listed in: http://www.perl.org/CGI_MetaFAQ.html
+
+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.
+
+The similarity between CGI response headers (defined in the CGI
+specification) and HTTP response headers (defined in the HTTP
+specification, RFC2616) is intentional, but can sometimes be confusing.
 
-The useful FAQs and related documents are:
+The CGI specification defines two kinds of script: the "Parsed Header"
+script, and the "Non Parsed Header" (NPH) script. Check your server
+documentation to see what it supports. "Parsed Header" scripts are
+simpler in various respects. The CGI specification allows any of the
+usual newline representations in the CGI response (it's the server's
+job to create an accurate HTTP response based on it). So "\n" written in
+text mode is technically correct, and recommended. NPH scripts are more
+tricky: they must put out a complete and accurate set of HTTP
+transaction response headers; the HTTP specification calls for records
+to be terminated with carriage-return and line-feed, i.e ASCII \015\012
+written in binary mode.
 
-    CGI FAQ
-        http://www.webthing.com/tutorials/cgifaq.html
+Using CGI.pm gives excellent platform independence, including EBCDIC
+systems. CGI.pm selects an appropriate newline representation
+($CGI::CRLF) and sets binmode as appropriate.
 
-    Web FAQ
-        http://www.boutell.com/faq/
+=head2 My CGI script runs from the command line but not the browser.  (500 Server Error)
 
-    WWW Security FAQ
-        http://www.w3.org/Security/Faq/
+Several things could be wrong.  You can go through the "Troubleshooting
+Perl CGI scripts" guide at
 
-    HTTP Spec
-        http://www.w3.org/pub/WWW/Protocols/HTTP/
+	http://www.perl.org/troubleshooting_CGI.html
 
-    HTML Spec
-        http://www.w3.org/TR/REC-html40/
-        http://www.w3.org/pub/WWW/MarkUp/
+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
+with HTTP or the CGI protocols).  Questions that appear to be Perl
+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
+listed in the CGI Meta FAQ:
 
-    CGI Spec
-        http://www.w3.org/CGI/
+	http://www.perl.org/CGI_MetaFAQ.html
 
-    CGI Security FAQ
-        http://www.go2net.com/people/paulp/cgi-security/safe-cgi.txt
 
 =head2 How can I get better error messages from a CGI program?
 
@@ -84,8 +109,8 @@ attempts to do a little simple formatting of the resulting plain text.
 Many folks attempt a simple-minded regular expression approach, like
 C<< s/<.*?>//g >>, but that fails in many cases because the tags
 may continue over line breaks, they may contain quoted angle-brackets,
-or HTML comment may be present.  Plus folks forget to convert
-entities, like C<&lt;> for example.
+or HTML comment may be present.  Plus, folks forget to convert
+entities--like C<&lt;> for example.
 
 Here's one "simple-minded" approach, that works for most files:
 
@@ -94,7 +119,7 @@ Here's one "simple-minded" approach, that works for most files:
 
 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
@@ -122,35 +147,68 @@ on text like this:
 
 =head2 How do I extract URLs?
 
-A quick but imperfect approach is
+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
+C<HTML::SimpleLinkExtor> as an example for something specifically
+suited to your needs.
+
+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.
+
+        #!/usr/bin/perl -n00
+        # qxurl - tchrist@perl.com
+        print "$2\n" while m{
+            < \s*
+              A \s+ HREF \s* = \s* (["']) (.*?) \1
+            \s* >
+        }gsix;
 
-    #!/usr/bin/perl -n00
-    # qxurl - tchrist@perl.com
-    print "$2\n" while m{
-	< \s*
-	  A \s+ HREF \s* = \s* (["']) (.*?) \1
-	\s* >
-    }gsix;
-
-This version does not adjust relative URLs, understand alternate
-bases, deal with HTML comments, deal with HREF and NAME attributes
-in the same tag, understand extra qualifiers like TARGET, or accept
-URLs themselves as arguments.  It also runs about 100x faster than a
-more "complete" solution using the LWP suite of modules, such as the
-http://www.perl.com/CPAN/authors/Tom_Christiansen/scripts/xurl.gz program.
 
 =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.
 
-=head2 How do I make a pop-up menu in HTML?
+See the section in the CGI.pm documentation on file uploads for code
+examples and details.
+
+=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?
 
@@ -186,6 +244,10 @@ through proxies:
 
 =head2 How do I automate an HTML form submission?
 
+If you are doing something complex, such as moving through many pages
+and forms or a web site, you can use C<WWW::Mechanize>.  See its
+documentation for all the details.
+
 If you're submitting values using the GET method, create a URL and encode
 the form using the C<query_form> method:
 
@@ -209,64 +271,75 @@ the content appropriately.
 
 =head2 How do I decode or create those %-encodings on the web?
 
-Here's an example of decoding:
+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
 
-    $string = "http://altavista.digital.com/cgi-bin/query?pg=q&what=news&fmt=.&q=%2Bcgi-bin+%2Bperl.exe";
-    $string =~ s/%([a-fA-F0-9]{2})/chr(hex($1))/ge;
+    s/%([A-Fa-f\d]{2})/chr hex $1/eg;                # decode
+	s/%([[:xdigit:]]{2})/chr hex $1/eg;          # same thing
 
-Encoding is a bit harder, because you can't just blindly change
-all characters that are not letters, digits or underscores (C<\W>)
-into their hex escapes.
-It's important that characters with special meaning like C</> and C<?>
-I<not> be translated.  Probably the easiest way to get this right is
-to avoid reinventing the wheel and just use the URI::Escape module,
-available from CPAN.
+However, you should only apply them to individual URI components, not
+the entire URI, otherwise you'll lose information and generally mess
+things up.  If that didn't explain it, don't worry.  Just go read
+section 2 of the RFC, it's probably the best explanation there is.
+
+RFC 2396 also contains a lot of other useful information, including a
+regexp for breaking any arbitrary URI into components (Appendix B).
 
 =head2 How do I redirect to another page?
 
-Instead of sending back a C<Content-Type> as the headers of your
-reply, send back a C<Location:> header.  Officially this should be a
-C<URI:> header, so the CGI.pm module (available from CPAN) sends back
-both:
+Specify the complete URL of the destination (even if it is on the same
+server). This is one of the two different kinds of CGI "Location:"
+responses which are defined in the CGI specification for a Parsed Headers
+script. The other kind (an absolute URLpath) is resolved internally to
+the server without any HTTP redirection. The CGI specifications do not
+allow relative URLs in either case.
 
-    Location: http://www.domain.com/newpage
-    URI: http://www.domain.com/newpage
+Use of CGI.pm is strongly recommended.  This example shows redirection
+with a complete URL. This redirection is handled by the web browser.
 
-Note that relative URLs in these headers can cause strange effects
-because of "optimizations" that servers do.
+      use CGI qw/:standard/;
 
-    $url = "http://www.perl.com/CPAN/";
-    print "Location: $url\n\n";
-    exit;
+      my $url = 'http://www.cpan.org/';
+      print redirect($url);
 
-To target a particular frame in a frameset, include the "Window-target:"
-in the header.
 
-    print <<EOF;
-    Location: http://www.domain.com/newpage
-    Window-target: <FrameName>
+This example shows a redirection with an absolute URLpath.  This
+redirection is handled by the local web server.
 
-    EOF
+      my $url = '/CPAN/index.html';
+      print redirect($url);
+
+
+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.
+
+      print "Location: $url\n";   # CGI response header
+      print "\n";                 # end of headers
 
-To be correct to the spec, each of those virtual newlines should really be
-physical C<"\015\012"> sequences by the time you hit the client browser.
-Except for NPH scripts, though, that local newline should get translated
-by your server into standard form, so you shouldn't have a problem
-here, even if you are stuck on MacOS.  Everybody else probably won't
-even notice.
 
 =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?
 
 The HTTPD::UserAdmin and HTTPD::GroupAdmin modules provide a
 consistent OO interface to these files, regardless of how they're
-stored.  Databases may be text, dbm, Berkley DB or any database with a
-DBI compatible driver.  HTTPD::UserAdmin supports files used by the
-`Basic' and `Digest' authentication schemes.  Here's an example:
+stored.  Databases may be text, dbm, Berkeley DB or any database with
+a DBI compatible driver.  HTTPD::UserAdmin supports files used by the
+"Basic" and "Digest" authentication schemes.  Here's an example:
 
     use HTTPD::UserAdmin ();
     HTTPD::UserAdmin
@@ -275,21 +348,14 @@ DBI compatible driver.  HTTPD::UserAdmin supports files used by the
 
 =head2 How do I make sure users can't enter values into a form that cause my CGI script to do bad things?
 
-Read the CGI security FAQ, at
-http://www-genome.wi.mit.edu/WWW/faqs/www-security-faq.html, and the
-Perl/CGI FAQ at
-http://www.perl.com/CPAN/doc/FAQs/cgi/perl-cgi-faq.html.
+See the security references listed in the CGI Meta FAQ
 
-In brief: use tainting (see L<perlsec>), which makes sure that data
-from outside your script (eg, CGI parameters) are never used in
-C<eval> or C<system> calls.  In addition to tainting, never use the
-single-argument form of system() or exec().  Instead, supply the
-command and arguments as a list, which prevents shell globbing.
+	http://www.perl.org/CGI_MetaFAQ.html
 
 =head2 How do I parse a mail header?
 
 For a quick-and-dirty solution, try this solution derived
-from page 222 of the 2nd edition of "Programming Perl":
+from L<perlfunc/split>:
 
     $/ = '';
     $header = <MSG>;
@@ -302,92 +368,110 @@ the Mail::Header module from CPAN (part of the MailTools package).
 
 =head2 How do I decode a CGI form?
 
-You use a standard module, probably CGI.pm.  Under no circumstances
-should you attempt to do so by hand!
-
-You'll see a lot of CGI programs that blindly read from STDIN the number
-of bytes equal to CONTENT_LENGTH for POSTs, or grab QUERY_STRING for
-decoding GETs.  These programs are very poorly written.  They only work
-sometimes.  They typically forget to check the return value of the read()
-system call, which is a cardinal sin.  They don't handle HEAD requests.
-They don't handle multipart forms used for file uploads.  They don't deal
-with GET/POST combinations where query fields are in more than one place.
-They don't deal with keywords in the query string.
-
-In short, they're bad hacks.  Resist them at all costs.  Please do not be
-tempted to reinvent the wheel.  Instead, use the CGI.pm or CGI_Lite.pm
-(available from CPAN), or if you're trapped in the module-free land
-of perl1 .. perl4, you might look into cgi-lib.pl (available from
-http://cgi-lib.stanford.edu/cgi-lib/ ).
-
-Make sure you know whether to use a GET or a POST in your form.
-GETs should only be used for something that doesn't update the server.
-Otherwise you can get mangled databases and repeated feedback mail
-messages.  The fancy word for this is ``idempotency''.  This simply
-means that there should be no difference between making a GET request
-for a particular URL once or multiple times.  This is because the
-HTTP protocol definition says that a GET request may be cached by the
-browser, or server, or an intervening proxy.  POST requests cannot be
-cached, because each request is independent and matters.  Typically,
-POST requests change or depend on state on the server (query or update
-a database, send mail, or purchase a computer).
+(contributed by brian d foy)
+
+Use the CGI.pm module that comes with Perl.  It's quick,
+it's easy, and it actually does quite a bit of work to
+ensure things happen correctly.  It handles GET, POST, and
+HEAD requests, multipart forms, multivalued fields, query
+string and message body combinations, and many other things
+you probably don't want to think about.
+
+It doesn't get much easier: the CGI module automatically
+parses the input and makes each value available through the
+C<param()> function.
+
+	use CGI qw(:standard);
+
+	my $total = param( 'price' ) + param( 'shipping' );
+
+	my @items = param( 'item' ); # multiple values, same field name
+
+If you want an object-oriented approach, CGI.pm can do that too.
+
+	use CGI;
+
+	my $cgi = CGI->new();
+
+	my $total = $cgi->param( 'price' ) + $cgi->param( 'shipping' );
+
+	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
+for you, too.
+
+Many people try to write their own decoder (or copy one from
+another program) and then run into one of the many "gotchas"
+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 hand 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.
-
-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 is not suggested.  Instead, see
-http://www.perl.com/CPAN/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
+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
 with the characters reversed, one added or subtracted to each digit, etc.
 
 =head2 How do I decode a MIME/BASE64 string?
 
-The MIME-tools package (available from CPAN) handles this and a lot
-more.  Decoding BASE64 becomes as simple as:
+The MIME-Base64 package (available from CPAN) handles this as well as
+the MIME/QP encoding.  Decoding BASE64 becomes as simple as:
 
-    use MIME::base64;
+    use MIME::Base64;
     $decoded = decode_base64($encoded);
 
-A more direct approach is to use the unpack() function's "u"
+The MIME-Tools package (available from CPAN) supports extraction with
+decoding of BASE64 encoded attachments and content directly from email
+messages.
+
+If the string to decode is short (less than 84 bytes long)
+a more direct approach is to use the unpack() function's "u"
 format after minor transliterations:
 
     tr#A-Za-z0-9+/##cd;                   # remove non-base64 chars
@@ -397,7 +481,7 @@ format after minor transliterations:
 
 =head2 How do I return the user's mail address?
 
-On systems that support getpwuid, the $< variable and the
+On systems that support getpwuid, the $< variable, and the
 Sys::Hostname module (which is part of the standard perl distribution),
 you can probably try using something like this:
 
@@ -459,22 +543,56 @@ Or you might be able use the CPAN module Mail::Mailer:
 The Mail::Internet module uses Net::SMTP which is less Unix-centric than
 Mail::Mailer, but less reliable.  Avoid raw SMTP commands.  There
 are many reasons to use a mail transport agent like sendmail.  These
-include queueing, MX records, and security.
+include queuing, MX records, and security.
+
+=head2 How do I use MIME to make an attachment to a mail message?
+
+This answer is extracted directly from the MIME::Lite documentation.
+Create a multipart message (i.e., one with attachments).
+
+    use MIME::Lite;
+
+    ### Create a new multipart message:
+    $msg = MIME::Lite->new(
+                 From    =>'me@myhost.com',
+                 To      =>'you@yourhost.com',
+                 Cc      =>'some@other.com, some@more.com',
+                 Subject =>'A message with 2 parts...',
+                 Type    =>'multipart/mixed'
+                 );
+
+    ### Add parts (each "attach" has same arguments as "new"):
+    $msg->attach(Type     =>'TEXT',
+                 Data     =>"Here's the GIF file you wanted"
+                 );
+    $msg->attach(Type     =>'image/gif',
+                 Path     =>'aaa000123.gif',
+                 Filename =>'logo.gif'
+                 );
+
+    $text = $msg->as_string;
+
+MIME::Lite also includes a method for sending these things.
+
+    $msg->send;
+
+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
-of the MailTools package), often a module is overkill, though.  Here's a
+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) || '';
         }
@@ -493,34 +611,42 @@ 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.
 
-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.
+	use Sys::Hostname;
 
-(We still need a good DNS domain name-learning method for non-Unix
-systems.)
+	$host = hostname();
+
+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.
+
+    use Socket;
+
+    my $address = inet_ntoa(
+    	scalar gethostbyname( $host || 'localhost' )
+    	);
 
 =head2 How do I fetch a news article or the active newsgroups?
 
 Use the Net::NNTP or News::NNTPClient modules, both available from CPAN.
-This can make tasks like fetching the newsgroup list as simple as:
+This can make tasks like fetching the newsgroup list as simple as
 
     perl -MNews::NNTPClient
       -e 'print News::NNTPClient->new->list("newsgroups")'
@@ -532,22 +658,26 @@ available from CPAN) is more complex but can put as well as fetch.
 
 =head2 How can I do RPC in Perl?
 
-A DCE::RPC module is being developed (but is not yet available), and
-will be released as part of the DCE-Perl package (available from
-CPAN).  The rpcgen suite, available from CPAN/authors/id/JAKE/, is
-an RPC stub generator and includes an RPC::ONC module.
+(Contributed by brian d foy)
+
+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) 1997-1999 Tom Christiansen and Nathan Torkington.
-All rights reserved.
+Copyright (c) 1997-2007 Tom Christiansen, Nathan Torkington, and
+other authors as noted. All rights reserved.
 
-When included as part of the Standard Version of Perl, or as part of
-its complete documentation whether printed or otherwise, this work
-may be distributed only under the terms of Perl's Artistic License.
-Any distribution of this file or derivatives thereof I<outside>
-of that package require that special arrangements be made with
-copyright holder.
+This documentation is free; you can redistribute it and/or modify it
+under the same terms as Perl itself.
 
 Irrespective of its distribution, all code examples in this file
 are hereby placed into the public domain.  You are permitted and