1perlfaq9(3) User Contributed Perl Documentation perlfaq9(3)
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6 perlfaq9 - Web, Email and Networking
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9 version 5.20201107
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12 This section deals with questions related to running web sites, sending
13 and receiving email as well as general networking.
14 Should I use a web framework?
16 Yes. If you are building a web site with any level of interactivity
17 (forms / users / databases), you will want to use a framework to make
18 handling requests and responses easier.
19 If there is no interactivity then you may still want to look at using
21 something like Template Toolkit <https://metacpan.org/module/Template>
22 or Plack::Middleware::TemplateToolkit so maintenance of your HTML files
23 (and other assets) is easier.
24 Which web framework should I use?
26 There is no simple answer to this question. Perl frameworks can run
27 everything from basic file servers and small scale intranets to massive
28 multinational multilingual websites that are the core to international
29 businesses.
30 Below is a list of a few frameworks with comments which might help you
32 in making a decision, depending on your specific requirements. Start by
33 reading the docs, then ask questions on the relevant mailing list or
34 IRC channel.
35 Catalyst
37 Strongly object-oriented and fully-featured with a long development
38 history and a large community and addon ecosystem. It is excellent
39 for large and complex applications, where you have full control
40 over the server.
41 Dancer2
43 Free of legacy weight, providing a lightweight and easy to learn
44 API. Has a growing addon ecosystem. It is best used for smaller
45 projects and very easy to learn for beginners.
46 Mojolicious
48 Self-contained and powerful for both small and larger projects,
49 with a focus on HTML5 and real-time web technologies such as
50 WebSockets.
51 Web::Simple
53 Strongly object-oriented and minimal, built for speed and intended
54 as a toolkit for building micro web apps, custom frameworks or for
55 tieing together existing Plack-compatible web applications with one
56 central dispatcher.
57 All of these interact with or use Plack which is worth understanding
59 the basics of when building a website in Perl (there is a lot of useful
60 Plack::Middleware
61 <https://metacpan.org/search?q=plack%3A%3Amiddleware>).
62 What is Plack and PSGI?
64 PSGI is the Perl Web Server Gateway Interface Specification, it is a
65 standard that many Perl web frameworks use, you should not need to
66 understand it to build a web site, the part you might want to use is
67 Plack.
68 Plack is a set of tools for using the PSGI stack. It contains
70 middleware <https://metacpan.org/search?q=plack%3A%3Amiddleware>
71 components, a reference server and utilities for Web application
72 frameworks. Plack is like Ruby's Rack or Python's Paste for WSGI.
73 You could build a web site using Plack and your own code, but for
75 anything other than a very basic web site, using a web framework (that
76 uses <https://plackperl.org>) is a better option.
77 How do I remove HTML from a string?
79 Use HTML::Strip, or HTML::FormatText which not only removes HTML but
80 also attempts to do a little simple formatting of the resulting plain
81 text.
82 How do I extract URLs?
84 HTML::SimpleLinkExtor will extract URLs from HTML, it handles anchors,
85 images, objects, frames, and many other tags that can contain a URL.
86 If you need anything more complex, you can create your own subclass of
87 HTML::LinkExtor or HTML::Parser. You might even use
88 HTML::SimpleLinkExtor as an example for something specifically suited
89 to your needs.
90 You can use URI::Find or URL::Search to extract URLs from an arbitrary
92 text document.
93 How do I fetch an HTML file?
95 (contributed by brian d foy)
96 The core HTTP::Tiny module can fetch web resources and give their
98 content back to you as a string:
99 use HTTP::Tiny;
101 my $ua = HTTP::Tiny->new;
103 my $html = $ua->get( "http://www.example.com/index.html" )->{content};
104 It can also store the resource directly in a file:
106 $ua->mirror( "http://www.example.com/index.html", "foo.html" );
108 If you need to do something more complicated, the HTTP::Tiny object can
110 be customized by setting attributes, or you can use LWP::UserAgent from
111 the libwww-perl distribution or Mojo::UserAgent from the Mojolicious
112 distribution to make common tasks easier. If you want to simulate an
113 interactive web browser, you can use the WWW::Mechanize module.
114 How do I automate an HTML form submission?
116 If you are doing something complex, such as moving through many pages
117 and forms or a web site, you can use WWW::Mechanize. See its
118 documentation for all the details.
119 If you're submitting values using the GET method, create a URL and
121 encode the form using the "www_form_urlencode" method from HTTP::Tiny:
122 use HTTP::Tiny;
124 my $ua = HTTP::Tiny->new;
126 my $query = $ua->www_form_urlencode([ q => 'DB_File', lucky => 1 ]);
128 my $url = "https://metacpan.org/search?$query";
129 my $content = $ua->get($url)->{content};
130 If you're using the POST method, the "post_form" method will encode the
132 content appropriately.
133 use HTTP::Tiny;
135 my $ua = HTTP::Tiny->new;
137 my $url = 'https://metacpan.org/search';
139 my $form = [ q => 'DB_File', lucky => 1 ];
140 my $content = $ua->post_form($url, $form)->{content};
141 How do I decode or create those %-encodings on the web?
143 Most of the time you should not need to do this as your web framework,
144 or if you are making a request, the LWP or other module would handle it
145 for you.
146 To encode a string yourself, use the URI::Escape module. The
148 "uri_escape" function returns the escaped string:
149 my $original = "Colon : Hash # Percent %";
151 my $escaped = uri_escape( $original );
153 print "$escaped\n"; # 'Colon%20%3A%20Hash%20%23%20Percent%20%25'
155 To decode the string, use the "uri_unescape" function:
157 my $unescaped = uri_unescape( $escaped );
159 print $unescaped; # back to original
161 Remember not to encode a full URI, you need to escape each component
163 separately and then join them together.
164 How do I redirect to another page?
166 Most Perl Web Frameworks will have a mechanism for doing this, using
167 the Catalyst framework it would be:
168 $c->res->redirect($url);
170 $c->detach();
171 If you are using Plack (which most frameworks do), then
173 Plack::Middleware::Rewrite is worth looking at if you are migrating
174 from Apache or have URL's you want to always redirect.
175 How do I put a password on my web pages?
177 See if the web framework you are using has an authentication system and
178 if that fits your needs.
179 Alternativly look at Plack::Middleware::Auth::Basic, or one of the
181 other Plack authentication <https://metacpan.org/search?q=plack+auth>
182 options.
183 How do I make sure users can't enter values into a form that causes my CGI
185 script to do bad things?
186 (contributed by brian d foy)
187 You can't prevent people from sending your script bad data. Even if you
189 add some client-side checks, people may disable them or bypass them
190 completely. For instance, someone might use a module such as LWP to
191 submit to your web site. If you want to prevent data that try to use
192 SQL injection or other sorts of attacks (and you should want to), you
193 have to not trust any data that enter your program.
194 The perlsec documentation has general advice about data security. If
196 you are using the DBI module, use placeholder to fill in data. If you
197 are running external programs with "system" or "exec", use the list
198 forms. There are many other precautions that you should take, too many
199 to list here, and most of them fall under the category of not using any
200 data that you don't intend to use. Trust no one.
201 How do I parse a mail header?
203 Use the Email::MIME module. It's well-tested and supports all the
204 craziness that you'll see in the real world (comment-folding
205 whitespace, encodings, comments, etc.).
206 use Email::MIME;
208 my $message = Email::MIME->new($rfc2822);
210 my $subject = $message->header('Subject');
211 my $from = $message->header('From');
212 If you've already got some other kind of email object, consider passing
214 it to Email::Abstract and then using its cast method to get an
215 Email::MIME object:
216 my $abstract = Email::Abstract->new($mail_message_object);
218 my $email_mime_object = $abstract->cast('Email::MIME');
219 How do I check a valid mail address?
221 (partly contributed by Aaron Sherman)
222 This isn't as simple a question as it sounds. There are two parts:
224 a) How do I verify that an email address is correctly formatted?
226 b) How do I verify that an email address targets a valid recipient?
228 Without sending mail to the address and seeing whether there's a human
230 on the other end to answer you, you cannot fully answer part b, but the
231 Email::Valid module will do both part a and part b as far as you can in
232 real-time.
233 Our best advice for verifying a person's mail address is to have them
235 enter their address twice, just as you normally do to change a
236 password. This usually weeds out typos. If both versions match, send
237 mail to that address with a personal message. If you get the message
238 back and they've followed your directions, you can be reasonably
239 assured that it's real.
240 A related strategy that's less open to forgery is to give them a PIN
242 (personal ID number). Record the address and PIN (best that it be a
243 random one) for later processing. In the mail you send, include a link
244 to your site with the PIN included. If the mail bounces, you know it's
245 not valid. If they don't click on the link, either they forged the
246 address or (assuming they got the message) following through wasn't
247 important so you don't need to worry about it.
248 How do I decode a MIME/BASE64 string?
250 The MIME::Base64 package handles this as well as the MIME/QP encoding.
251 Decoding base 64 becomes as simple as:
252 use MIME::Base64;
254 my $decoded = decode_base64($encoded);
255 The Email::MIME module can decode base 64-encoded email message parts
257 transparently so the developer doesn't need to worry about it.
258 How do I find the user's mail address?
260 Ask them for it. There are so many email providers available that it's
261 unlikely the local system has any idea how to determine a user's email
262 address.
263 The exception is for organization-specific email (e.g.
265 foo@yourcompany.com) where policy can be codified in your program. In
266 that case, you could look at $ENV{USER}, $ENV{LOGNAME}, and
267 getpwuid($<) in scalar context, like so:
268 my $user_name = getpwuid($<)
270 But you still cannot make assumptions about whether this is correct,
272 unless your policy says it is. You really are best off asking the user.
273 How do I send email?
275 Use the Email::Stuffer module, like so:
276 # first, create your message
278 my $message = Email::Stuffer->from('you@example.com')
279 ->to('friend@example.com')
280 ->subject('Happy birthday!')
281 ->text_body("Happy birthday to you!\n");
282 $message->send_or_die;
284 By default, Email::Sender::Simple (the "send" and "send_or_die" methods
286 use this under the hood) will try "sendmail" first, if it exists in
287 your $PATH. This generally isn't the case. If there's a remote mail
288 server you use to send mail, consider investigating one of the
289 Transport classes. At time of writing, the available transports
290 include:
291 Email::Sender::Transport::Sendmail
293 This is the default. If you can use the mail(1) or mailx(1) program
294 to send mail from the machine where your code runs, you should be
295 able to use this.
296 Email::Sender::Transport::SMTP
298 This transport contacts a remote SMTP server over TCP. It
299 optionally uses TLS or SSL and can authenticate to the server via
300 SASL.
301 Telling Email::Stuffer to use your transport is straightforward.
303 $message->transport($email_sender_transport_object)->send_or_die;
305 How do I use MIME to make an attachment to a mail message?
307 Email::MIME directly supports multipart messages. Email::MIME objects
308 themselves are parts and can be attached to other Email::MIME objects.
309 Consult the Email::MIME documentation for more information, including
310 all of the supported methods and examples of their use.
311 Email::Stuffer uses Email::MIME under the hood to construct messages,
313 and wraps the most common attachment tasks with the simple "attach" and
314 "attach_file" methods.
315 Email::Stuffer->to('friend@example.com')
317 ->subject('The file')
318 ->attach_file('stuff.csv')
319 ->send_or_die;
320 How do I read email?
322 Use the Email::Folder module, like so:
323 use Email::Folder;
325 my $folder = Email::Folder->new('/path/to/email/folder');
327 while(my $message = $folder->next_message) {
328 # next_message returns Email::Simple objects, but we want
329 # Email::MIME objects as they're more robust
330 my $mime = Email::MIME->new($message->as_string);
331 }
332 There are different classes in the Email::Folder namespace for
334 supporting various mailbox types. Note that these modules are generally
335 rather limited and only support reading rather than writing.
336 How do I find out my hostname, domainname, or IP address?
338 (contributed by brian d foy)
339 The Net::Domain module, which is part of the Standard Library starting
341 in Perl 5.7.3, can get you the fully qualified domain name (FQDN), the
342 host name, or the domain name.
343 use Net::Domain qw(hostname hostfqdn hostdomain);
345 my $host = hostfqdn();
347 The Sys::Hostname module, part of the Standard Library, can also get
349 the hostname:
350 use Sys::Hostname;
352 $host = hostname();
354 The Sys::Hostname::Long module takes a different approach and tries
356 harder to return the fully qualified hostname:
357 use Sys::Hostname::Long 'hostname_long';
359 my $hostname = hostname_long();
361 To get the IP address, you can use the "gethostbyname" built-in
363 function to turn the name into a number. To turn that number into the
364 dotted octet form (a.b.c.d) that most people expect, use the
365 "inet_ntoa" function from the Socket module, which also comes with
366 perl.
367 use Socket;
369 my $address = inet_ntoa(
371 scalar gethostbyname( $host || 'localhost' )
372 );
373 How do I fetch/put an (S)FTP file?
375 Net::FTP, and Net::SFTP allow you to interact with FTP and SFTP (Secure
376 FTP) servers.
377 How can I do RPC in Perl?
379 Use one of the RPC modules( <https://metacpan.org/search?q=RPC> ).
380
382 Copyright (c) 1997-2010 Tom Christiansen, Nathan Torkington, and other
383 authors as noted. All rights reserved.
384 This documentation is free; you can redistribute it and/or modify it
386 under the same terms as Perl itself.
387 Irrespective of its distribution, all code examples in this file are
389 hereby placed into the public domain. You are permitted and encouraged
390 to use this code in your own programs for fun or for profit as you see
391 fit. A simple comment in the code giving credit would be courteous but
392 is not required.
393perl v5.32.0 2020-11-09 perlfaq9(3)