1perlfaq9(3) User Contributed Perl Documentation perlfaq9(3)
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6 perlfaq9 - Web, Email and Networking
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9 version 5.20180605
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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 Dancer
43 Young and free of legacy weight, providing a lightweight and easy
44 to learn API. Has a growing addon ecosystem. It is best used for
45 smaller projects and very easy to learn for beginners.
46 Mojolicious
48 Fairly young with a focus on HTML5 and real-time web technologies
49 such as WebSockets.
50 Web::Simple
52 Currently experimental, strongly object-oriented, built for speed
53 and intended as a toolkit for building micro web apps, custom
54 frameworks or for tieing together existing Plack-compatible web
55 applications with one central dispatcher.
56 All of these interact with or use Plack which is worth understanding
58 the basics of when building a website in Perl (there is a lot of useful
59 Plack::Middleware
60 <https://metacpan.org/search?q=plack%3A%3Amiddleware>).
61 What is Plack and PSGI?
63 PSGI is the Perl Web Server Gateway Interface Specification, it is a
64 standard that many Perl web frameworks use, you should not need to
65 understand it to build a web site, the part you might want to use is
66 Plack.
67 Plack is a set of tools for using the PSGI stack. It contains
69 middleware <https://metacpan.org/search?q=plack%3A%3Amiddleware>
70 components, a reference server and utilities for Web application
71 frameworks. Plack is like Ruby's Rack or Python's Paste for WSGI.
72 You could build a web site using Plack and your own code, but for
74 anything other than a very basic web site, using a web framework (that
75 uses Plack) is a better option.
76 How do I remove HTML from a string?
78 Use HTML::Strip, or HTML::FormatText which not only removes HTML but
79 also attempts to do a little simple formatting of the resulting plain
80 text.
81 How do I extract URLs?
83 HTML::SimpleLinkExtor will extract URLs from HTML, it handles anchors,
84 images, objects, frames, and many other tags that can contain a URL.
85 If you need anything more complex, you can create your own subclass of
86 HTML::LinkExtor or HTML::Parser. You might even use
87 HTML::SimpleLinkExtor as an example for something specifically suited
88 to your needs.
89 You can use URI::Find to extract URLs from an arbitrary text document.
91 How do I fetch an HTML file?
93 (contributed by brian d foy)
94 Use the libwww-perl distribution. The LWP::Simple module can fetch web
96 resources and give their content back to you as a string:
97 use LWP::Simple qw(get);
99 my $html = get( "http://www.example.com/index.html" );
101 It can also store the resource directly in a file:
103 use LWP::Simple qw(getstore);
105 getstore( "http://www.example.com/index.html", "foo.html" );
107 If you need to do something more complicated, you can use
109 LWP::UserAgent module to create your own user-agent (e.g. browser) to
110 get the job done. If you want to simulate an interactive web browser,
111 you can use the WWW::Mechanize module.
112 How do I automate an HTML form submission?
114 If you are doing something complex, such as moving through many pages
115 and forms or a web site, you can use WWW::Mechanize. See its
116 documentation for all the details.
117 If you're submitting values using the GET method, create a URL and
119 encode the form using the "query_form" method:
120 use LWP::Simple;
122 use URI::URL;
123 my $url = url('L<http://www.perl.com/cgi-bin/cpan_mod')>;
125 $url->query_form(module => 'DB_File', readme => 1);
126 $content = get($url);
127 If you're using the POST method, create your own user agent and encode
129 the content appropriately.
130 use HTTP::Request::Common qw(POST);
132 use LWP::UserAgent;
133 my $ua = LWP::UserAgent->new();
135 my $req = POST 'L<http://www.perl.com/cgi-bin/cpan_mod'>,
136 [ module => 'DB_File', readme => 1 ];
137 my $content = $ua->request($req)->as_string;
138 How do I decode or create those %-encodings on the web?
140 Most of the time you should not need to do this as your web framework,
141 or if you are making a request, the LWP or other module would handle it
142 for you.
143 To encode a string yourself, use the URI::Escape module. The
145 "uri_escape" function returns the escaped string:
146 my $original = "Colon : Hash # Percent %";
148 my $escaped = uri_escape( $original );
150 print "$escaped\n"; # 'Colon%20%3A%20Hash%20%23%20Percent%20%25'
152 To decode the string, use the "uri_unescape" function:
154 my $unescaped = uri_unescape( $escaped );
156 print $unescaped; # back to original
158 Remember not to encode a full URI, you need to escape each component
160 separately and then join them together.
161 How do I redirect to another page?
163 Most Perl Web Frameworks will have a mechanism for doing this, using
164 the Catalyst framework it would be:
165 $c->res->redirect($url);
167 $c->detach();
168 If you are using Plack (which most frameworks do), then
170 Plack::Middleware::Rewrite is worth looking at if you are migrating
171 from Apache or have URL's you want to always redirect.
172 How do I put a password on my web pages?
174 See if the web framework you are using has an authentication system and
175 if that fits your needs.
176 Alternativly look at Plack::Middleware::Auth::Basic, or one of the
178 other Plack authentication <https://metacpan.org/search?q=plack+auth>
179 options.
180 How do I make sure users can't enter values into a form that causes my CGI
182 script to do bad things?
183 (contributed by brian d foy)
184 You can't prevent people from sending your script bad data. Even if you
186 add some client-side checks, people may disable them or bypass them
187 completely. For instance, someone might use a module such as LWP to
188 submit to your web site. If you want to prevent data that try to use
189 SQL injection or other sorts of attacks (and you should want to), you
190 have to not trust any data that enter your program.
191 The perlsec documentation has general advice about data security. If
193 you are using the DBI module, use placeholder to fill in data. If you
194 are running external programs with "system" or "exec", use the list
195 forms. There are many other precautions that you should take, too many
196 to list here, and most of them fall under the category of not using any
197 data that you don't intend to use. Trust no one.
198 How do I parse a mail header?
200 Use the Email::MIME module. It's well-tested and supports all the
201 craziness that you'll see in the real world (comment-folding
202 whitespace, encodings, comments, etc.).
203 use Email::MIME;
205 my $message = Email::MIME->new($rfc2822);
207 my $subject = $message->header('Subject');
208 my $from = $message->header('From');
209 If you've already got some other kind of email object, consider passing
211 it to Email::Abstract and then using its cast method to get an
212 Email::MIME object:
213 my $abstract = Email::Abstract->new($mail_message_object);
215 my $email_mime_object = $abstract->cast('Email::MIME');
216 How do I check a valid mail address?
218 (partly contributed by Aaron Sherman)
219 This isn't as simple a question as it sounds. There are two parts:
221 a) How do I verify that an email address is correctly formatted?
223 b) How do I verify that an email address targets a valid recipient?
225 Without sending mail to the address and seeing whether there's a human
227 on the other end to answer you, you cannot fully answer part b, but the
228 Email::Valid module will do both part a and part b as far as you can in
229 real-time.
230 Our best advice for verifying a person's mail address is to have them
232 enter their address twice, just as you normally do to change a
233 password. This usually weeds out typos. If both versions match, send
234 mail to that address with a personal message. If you get the message
235 back and they've followed your directions, you can be reasonably
236 assured that it's real.
237 A related strategy that's less open to forgery is to give them a PIN
239 (personal ID number). Record the address and PIN (best that it be a
240 random one) for later processing. In the mail you send, include a link
241 to your site with the PIN included. If the mail bounces, you know it's
242 not valid. If they don't click on the link, either they forged the
243 address or (assuming they got the message) following through wasn't
244 important so you don't need to worry about it.
245 How do I decode a MIME/BASE64 string?
247 The MIME::Base64 package handles this as well as the MIME/QP encoding.
248 Decoding base 64 becomes as simple as:
249 use MIME::Base64;
251 my $decoded = decode_base64($encoded);
252 The Email::MIME module can decode base 64-encoded email message parts
254 transparently so the developer doesn't need to worry about it.
255 How do I find the user's mail address?
257 Ask them for it. There are so many email providers available that it's
258 unlikely the local system has any idea how to determine a user's email
259 address.
260 The exception is for organization-specific email (e.g.
262 foo@yourcompany.com) where policy can be codified in your program. In
263 that case, you could look at $ENV{USER}, $ENV{LOGNAME}, and
264 getpwuid($<) in scalar context, like so:
265 my $user_name = getpwuid($<)
267 But you still cannot make assumptions about whether this is correct,
269 unless your policy says it is. You really are best off asking the user.
270 How do I send email?
272 Use the Email::MIME and Email::Sender::Simple modules, like so:
273 # first, create your message
275 my $message = Email::MIME->create(
276 header_str => [
277 From => 'you@example.com',
278 To => 'friend@example.com',
279 Subject => 'Happy birthday!',
280 ],
281 attributes => {
282 encoding => 'quoted-printable',
283 charset => 'utf-8',
284 },
285 body_str => "Happy birthday to you!\n",
286 );
287 use Email::Sender::Simple qw(sendmail);
289 sendmail($message);
290 By default, Email::Sender::Simple will try `sendmail` first, if it
292 exists in your $PATH. This generally isn't the case. If there's a
293 remote mail server you use to send mail, consider investigating one of
294 the Transport classes. At time of writing, the available transports
295 include:
296 Email::Sender::Transport::Sendmail
298 This is the default. If you can use the mail(1) or mailx(1) program
299 to send mail from the machine where your code runs, you should be
300 able to use this.
301 Email::Sender::Transport::SMTP
303 This transport contacts a remote SMTP server over TCP. It
304 optionally uses TLS or SSL and can authenticate to the server via
305 SASL.
306 Telling Email::Sender::Simple to use your transport is straightforward.
308 sendmail(
310 $message,
311 {
312 transport => $email_sender_transport_object,
313 }
314 );
315 How do I use MIME to make an attachment to a mail message?
317 Email::MIME directly supports multipart messages. Email::MIME objects
318 themselves are parts and can be attached to other Email::MIME objects.
319 Consult the Email::MIME documentation for more information, including
320 all of the supported methods and examples of their use.
321 How do I read email?
323 Use the Email::Folder module, like so:
324 use Email::Folder;
326 my $folder = Email::Folder->new('/path/to/email/folder');
328 while(my $message = $folder->next_message) {
329 # next_message returns Email::Simple objects, but we want
330 # Email::MIME objects as they're more robust
331 my $mime = Email::MIME->new($message->as_string);
332 }
333 There are different classes in the Email::Folder namespace for
335 supporting various mailbox types. Note that these modules are generally
336 rather limited and only support reading rather than writing.
337 How do I find out my hostname, domainname, or IP address?
339 (contributed by brian d foy)
340 The Net::Domain module, which is part of the Standard Library starting
342 in Perl 5.7.3, can get you the fully qualified domain name (FQDN), the
343 host name, or the domain name.
344 use Net::Domain qw(hostname hostfqdn hostdomain);
346 my $host = hostfqdn();
348 The Sys::Hostname module, part of the Standard Library, can also get
350 the hostname:
351 use Sys::Hostname;
353 $host = hostname();
355 The Sys::Hostname::Long module takes a different approach and tries
357 harder to return the fully qualified hostname:
358 use Sys::Hostname::Long 'hostname_long';
360 my $hostname = hostname_long();
362 To get the IP address, you can use the "gethostbyname" built-in
364 function to turn the name into a number. To turn that number into the
365 dotted octet form (a.b.c.d) that most people expect, use the
366 "inet_ntoa" function from the Socket module, which also comes with
367 perl.
368 use Socket;
370 my $address = inet_ntoa(
372 scalar gethostbyname( $host || 'localhost' )
373 );
374 How do I fetch/put an (S)FTP file?
376 Net::FTP, and Net::SFTP allow you to interact with FTP and SFTP (Secure
377 FTP) servers.
378 How can I do RPC in Perl?
380 Use one of the RPC modules( <https://metacpan.org/search?q=RPC> ).
381
383 Copyright (c) 1997-2010 Tom Christiansen, Nathan Torkington, and other
384 authors as noted. All rights reserved.
385 This documentation is free; you can redistribute it and/or modify it
387 under the same terms as Perl itself.
388 Irrespective of its distribution, all code examples in this file are
390 hereby placed into the public domain. You are permitted and encouraged
391 to use this code in your own programs for fun or for profit as you see
392 fit. A simple comment in the code giving credit would be courteous but
393 is not required.
394perl v5.26.3 2018-06-05 perlfaq9(3)