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68dc0745 | 1 | =head1 NAME |
2 | ||
5cd0b561 | 3 | perlfaq9 - Networking ($Revision: 1.15 $, $Date: 2003/01/31 17:36:57 $) |
68dc0745 | 4 | |
5 | =head1 DESCRIPTION | |
6 | ||
7 | This section deals with questions related to networking, the internet, | |
8 | and a few on the web. | |
9 | ||
24f1ba9b | 10 | =head2 What is the correct form of response from a CGI script? |
68dc0745 | 11 | |
24f1ba9b JH |
12 | (Alan Flavell <flavell+www@a5.ph.gla.ac.uk> answers...) |
13 | ||
197aec24 RGS |
14 | The Common Gateway Interface (CGI) specifies a software interface between |
15 | a program ("CGI script") and a web server (HTTPD). It is not specific | |
16 | to Perl, and has its own FAQs and tutorials, and usenet group, | |
17 | comp.infosystems.www.authoring.cgi | |
24f1ba9b | 18 | |
1577cd80 | 19 | The original CGI specification is at: http://hoohoo.ncsa.uiuc.edu/cgi/ |
24f1ba9b | 20 | |
1577cd80 | 21 | Current best-practice RFC draft at: http://CGI-Spec.Golux.Com/ |
24f1ba9b JH |
22 | |
23 | Other relevant documentation listed in: http://www.perl.org/CGI_MetaFAQ.html | |
68dc0745 | 24 | |
197aec24 | 25 | These Perl FAQs very selectively cover some CGI issues. However, Perl |
24f1ba9b | 26 | programmers are strongly advised to use the CGI.pm module, to take care |
197aec24 | 27 | of the details for them. |
68dc0745 | 28 | |
24f1ba9b JH |
29 | The similarity between CGI response headers (defined in the CGI |
30 | specification) and HTTP response headers (defined in the HTTP | |
31 | specification, RFC2616) is intentional, but can sometimes be confusing. | |
68dc0745 | 32 | |
24f1ba9b JH |
33 | The CGI specification defines two kinds of script: the "Parsed Header" |
34 | script, and the "Non Parsed Header" (NPH) script. Check your server | |
35 | documentation to see what it supports. "Parsed Header" scripts are | |
36 | simpler in various respects. The CGI specification allows any of the | |
37 | usual newline representations in the CGI response (it's the server's | |
38 | job to create an accurate HTTP response based on it). So "\n" written in | |
39 | text mode is technically correct, and recommended. NPH scripts are more | |
40 | tricky: they must put out a complete and accurate set of HTTP | |
41 | transaction response headers; the HTTP specification calls for records | |
42 | to be terminated with carriage-return and line-feed, i.e ASCII \015\012 | |
43 | written in binary mode. | |
68dc0745 | 44 | |
24f1ba9b JH |
45 | Using CGI.pm gives excellent platform independence, including EBCDIC |
46 | systems. CGI.pm selects an appropriate newline representation | |
47 | ($CGI::CRLF) and sets binmode as appropriate. | |
c8db1d39 | 48 | |
24f1ba9b | 49 | =head2 My CGI script runs from the command line but not the browser. (500 Server Error) |
c8db1d39 | 50 | |
0bc0ad85 JH |
51 | Several things could be wrong. You can go through the "Troubleshooting |
52 | Perl CGI scripts" guide at | |
53 | ||
54 | http://www.perl.org/troubleshooting_CGI.html | |
55 | ||
197aec24 | 56 | If, after that, you can demonstrate that you've read the FAQs and that |
24f1ba9b JH |
57 | your problem isn't something simple that can be easily answered, you'll |
58 | probably receive a courteous and useful reply to your question if you | |
59 | post it on comp.infosystems.www.authoring.cgi (if it's something to do | |
60 | with HTTP or the CGI protocols). Questions that appear to be Perl | |
61 | questions but are really CGI ones that are posted to comp.lang.perl.misc | |
62 | are not so well received. | |
c8db1d39 | 63 | |
197aec24 | 64 | The useful FAQs, related documents, and troubleshooting guides are |
24f1ba9b JH |
65 | listed in the CGI Meta FAQ: |
66 | ||
67 | http://www.perl.org/CGI_MetaFAQ.html | |
c8db1d39 | 68 | |
c8db1d39 TC |
69 | |
70 | =head2 How can I get better error messages from a CGI program? | |
71 | ||
72 | Use the CGI::Carp module. It replaces C<warn> and C<die>, plus the | |
73 | normal Carp modules C<carp>, C<croak>, and C<confess> functions with | |
74 | more verbose and safer versions. It still sends them to the normal | |
75 | server error log. | |
76 | ||
77 | use CGI::Carp; | |
78 | warn "This is a complaint"; | |
79 | die "But this one is serious"; | |
80 | ||
81 | The following use of CGI::Carp also redirects errors to a file of your choice, | |
82 | placed in a BEGIN block to catch compile-time warnings as well: | |
83 | ||
84 | BEGIN { | |
85 | use CGI::Carp qw(carpout); | |
86 | open(LOG, ">>/var/local/cgi-logs/mycgi-log") | |
87 | or die "Unable to append to mycgi-log: $!\n"; | |
88 | carpout(*LOG); | |
89 | } | |
90 | ||
91 | You can even arrange for fatal errors to go back to the client browser, | |
92 | which is nice for your own debugging, but might confuse the end user. | |
93 | ||
94 | use CGI::Carp qw(fatalsToBrowser); | |
95 | die "Bad error here"; | |
96 | ||
97 | Even if the error happens before you get the HTTP header out, the module | |
98 | will try to take care of this to avoid the dreaded server 500 errors. | |
99 | Normal warnings still go out to the server error log (or wherever | |
100 | you've sent them with C<carpout>) with the application name and date | |
101 | stamp prepended. | |
102 | ||
68dc0745 | 103 | =head2 How do I remove HTML from a string? |
104 | ||
f29c64d6 | 105 | The most correct way (albeit not the fastest) is to use HTML::Parser |
bed171df | 106 | from CPAN. Another mostly correct |
7d7e76cf MS |
107 | way is to use HTML::FormatText which not only removes HTML but also |
108 | attempts to do a little simple formatting of the resulting plain text. | |
68dc0745 | 109 | |
110 | Many folks attempt a simple-minded regular expression approach, like | |
c47ff5f1 | 111 | C<< s/<.*?>//g >>, but that fails in many cases because the tags |
68dc0745 | 112 | may continue over line breaks, they may contain quoted angle-brackets, |
a6dd486b JB |
113 | or HTML comment may be present. Plus, folks forget to convert |
114 | entities--like C<<> for example. | |
68dc0745 | 115 | |
116 | Here's one "simple-minded" approach, that works for most files: | |
117 | ||
118 | #!/usr/bin/perl -p0777 | |
119 | s/<(?:[^>'"]*|(['"]).*?\1)*>//gs | |
120 | ||
121 | If you want a more complete solution, see the 3-stage striphtml | |
122 | program in | |
a93751fa | 123 | http://www.cpan.org/authors/Tom_Christiansen/scripts/striphtml.gz |
68dc0745 | 124 | . |
125 | ||
c8db1d39 TC |
126 | Here are some tricky cases that you should think about when picking |
127 | a solution: | |
128 | ||
129 | <IMG SRC = "foo.gif" ALT = "A > B"> | |
130 | ||
d92eb7b0 | 131 | <IMG SRC = "foo.gif" |
c8db1d39 TC |
132 | ALT = "A > B"> |
133 | ||
134 | <!-- <A comment> --> | |
135 | ||
136 | <script>if (a<b && a>c)</script> | |
137 | ||
138 | <# Just data #> | |
139 | ||
140 | <![INCLUDE CDATA [ >>>>>>>>>>>> ]]> | |
141 | ||
142 | If HTML comments include other tags, those solutions would also break | |
143 | on text like this: | |
144 | ||
145 | <!-- This section commented out. | |
146 | <B>You can't see me!</B> | |
147 | --> | |
148 | ||
68dc0745 | 149 | =head2 How do I extract URLs? |
150 | ||
e67d034e JH |
151 | You can easily extract all sorts of URLs from HTML with |
152 | C<HTML::SimpleLinkExtor> which handles anchors, images, objects, | |
197aec24 RGS |
153 | frames, and many other tags that can contain a URL. If you need |
154 | anything more complex, you can create your own subclass of | |
155 | C<HTML::LinkExtor> or C<HTML::Parser>. You might even use | |
e67d034e JH |
156 | C<HTML::SimpleLinkExtor> as an example for something specifically |
157 | suited to your needs. | |
158 | ||
49d635f9 RGS |
159 | You can use URI::Find to extract URLs from an arbitrary text document. |
160 | ||
197aec24 | 161 | Less complete solutions involving regular expressions can save |
e67d034e JH |
162 | you a lot of processing time if you know that the input is simple. One |
163 | solution from Tom Christiansen runs 100 times faster than most | |
164 | module based approaches but only extracts URLs from anchors where the first | |
197aec24 | 165 | attribute is HREF and there are no other attributes. |
e67d034e JH |
166 | |
167 | #!/usr/bin/perl -n00 | |
168 | # qxurl - tchrist@perl.com | |
169 | print "$2\n" while m{ | |
170 | < \s* | |
171 | A \s+ HREF \s* = \s* (["']) (.*?) \1 | |
172 | \s* > | |
173 | }gsix; | |
174 | ||
68dc0745 | 175 | |
176 | =head2 How do I download a file from the user's machine? How do I open a file on another machine? | |
177 | ||
49d635f9 RGS |
178 | In this case, download means to use the file upload feature of HTML |
179 | forms. You allow the web surfer to specify a file to send to your web | |
180 | server. To you it looks like a download, and to the user it looks | |
181 | like an upload. No matter what you call it, you do it with what's | |
182 | known as B<multipart/form-data> encoding. The CGI.pm module (which | |
183 | comes with Perl as part of the Standard Library) supports this in the | |
184 | start_multipart_form() method, which isn't the same as the startform() | |
185 | method. | |
186 | ||
187 | See the section in the CGI.pm documentation on file uploads for code | |
188 | examples and details. | |
68dc0745 | 189 | |
190 | =head2 How do I make a pop-up menu in HTML? | |
191 | ||
c47ff5f1 | 192 | Use the B<< <SELECT> >> and B<< <OPTION> >> tags. The CGI.pm |
68dc0745 | 193 | module (available from CPAN) supports this widget, as well as many |
194 | others, including some that it cleverly synthesizes on its own. | |
195 | ||
196 | =head2 How do I fetch an HTML file? | |
197 | ||
46fc3d4c | 198 | One approach, if you have the lynx text-based HTML browser installed |
199 | on your system, is this: | |
68dc0745 | 200 | |
201 | $html_code = `lynx -source $url`; | |
202 | $text_data = `lynx -dump $url`; | |
203 | ||
d92eb7b0 GS |
204 | The libwww-perl (LWP) modules from CPAN provide a more powerful way |
205 | to do this. They don't require lynx, but like lynx, can still work | |
206 | through proxies: | |
46fc3d4c | 207 | |
c8db1d39 TC |
208 | # simplest version |
209 | use LWP::Simple; | |
210 | $content = get($URL); | |
211 | ||
212 | # or print HTML from a URL | |
46fc3d4c | 213 | use LWP::Simple; |
6cecdcac | 214 | getprint "http://www.linpro.no/lwp/"; |
46fc3d4c | 215 | |
c8db1d39 | 216 | # or print ASCII from HTML from a URL |
65acb1b1 | 217 | # also need HTML-Tree package from CPAN |
46fc3d4c | 218 | use LWP::Simple; |
f29c64d6 | 219 | use HTML::Parser; |
46fc3d4c | 220 | use HTML::FormatText; |
221 | my ($html, $ascii); | |
222 | $html = get("http://www.perl.com/"); | |
223 | defined $html | |
224 | or die "Can't fetch HTML from http://www.perl.com/"; | |
225 | $ascii = HTML::FormatText->new->format(parse_html($html)); | |
226 | print $ascii; | |
227 | ||
c8db1d39 TC |
228 | =head2 How do I automate an HTML form submission? |
229 | ||
230 | If you're submitting values using the GET method, create a URL and encode | |
231 | the form using the C<query_form> method: | |
232 | ||
233 | use LWP::Simple; | |
234 | use URI::URL; | |
235 | ||
236 | my $url = url('http://www.perl.com/cgi-bin/cpan_mod'); | |
237 | $url->query_form(module => 'DB_File', readme => 1); | |
238 | $content = get($url); | |
239 | ||
240 | If you're using the POST method, create your own user agent and encode | |
241 | the content appropriately. | |
242 | ||
243 | use HTTP::Request::Common qw(POST); | |
244 | use LWP::UserAgent; | |
245 | ||
246 | $ua = LWP::UserAgent->new(); | |
247 | my $req = POST 'http://www.perl.com/cgi-bin/cpan_mod', | |
248 | [ module => 'DB_File', readme => 1 ]; | |
249 | $content = $ua->request($req)->as_string; | |
250 | ||
251 | =head2 How do I decode or create those %-encodings on the web? | |
68dc0745 | 252 | |
68dc0745 | 253 | |
575cc754 JH |
254 | If you are writing a CGI script, you should be using the CGI.pm module |
255 | that comes with perl, or some other equivalent module. The CGI module | |
256 | automatically decodes queries for you, and provides an escape() | |
257 | function to handle encoding. | |
68dc0745 | 258 | |
575cc754 JH |
259 | |
260 | The best source of detailed information on URI encoding is RFC 2396. | |
261 | Basically, the following substitutions do it: | |
262 | ||
48a4adce | 263 | s/([^\w()'*~!.-])/sprintf '%%%02x', ord $1/eg; # encode |
575cc754 | 264 | |
f05bbc40 | 265 | s/%([A-Fa-f\d]{2})/chr hex $1/eg; # decode |
575cc754 JH |
266 | |
267 | However, you should only apply them to individual URI components, not | |
268 | the entire URI, otherwise you'll lose information and generally mess | |
269 | things up. If that didn't explain it, don't worry. Just go read | |
270 | section 2 of the RFC, it's probably the best explanation there is. | |
271 | ||
272 | RFC 2396 also contains a lot of other useful information, including a | |
273 | regexp for breaking any arbitrary URI into components (Appendix B). | |
68dc0745 | 274 | |
275 | =head2 How do I redirect to another page? | |
276 | ||
24f1ba9b JH |
277 | Specify the complete URL of the destination (even if it is on the same |
278 | server). This is one of the two different kinds of CGI "Location:" | |
279 | responses which are defined in the CGI specification for a Parsed Headers | |
280 | script. The other kind (an absolute URLpath) is resolved internally to | |
281 | the server without any HTTP redirection. The CGI specifications do not | |
282 | allow relative URLs in either case. | |
283 | ||
284 | Use of CGI.pm is strongly recommended. This example shows redirection | |
285 | with a complete URL. This redirection is handled by the web browser. | |
286 | ||
287 | use CGI qw/:standard/; | |
288 | ||
a93751fa | 289 | my $url = 'http://www.cpan.org/'; |
24f1ba9b | 290 | print redirect($url); |
68dc0745 | 291 | |
68dc0745 | 292 | |
24f1ba9b JH |
293 | This example shows a redirection with an absolute URLpath. This |
294 | redirection is handled by the local web server. | |
68dc0745 | 295 | |
24f1ba9b JH |
296 | my $url = '/CPAN/index.html'; |
297 | print redirect($url); | |
c8db1d39 | 298 | |
d92eb7b0 | 299 | |
197aec24 | 300 | But if coded directly, it could be as follows (the final "\n" is |
24f1ba9b | 301 | shown separately, for clarity), using either a complete URL or |
197aec24 | 302 | an absolute URLpath. |
d92eb7b0 | 303 | |
24f1ba9b JH |
304 | print "Location: $url\n"; # CGI response header |
305 | print "\n"; # end of headers | |
d92eb7b0 | 306 | |
c8db1d39 | 307 | |
68dc0745 | 308 | =head2 How do I put a password on my web pages? |
309 | ||
49d635f9 RGS |
310 | To enable authentication for your web server, you need to configure |
311 | your web server. The configuration is different for different sorts | |
312 | of web servers---apache does it differently from iPlanet which does | |
313 | it differently from IIS. Check your web server documentation for | |
314 | the details for your particular server. | |
68dc0745 | 315 | |
316 | =head2 How do I edit my .htpasswd and .htgroup files with Perl? | |
317 | ||
318 | The HTTPD::UserAdmin and HTTPD::GroupAdmin modules provide a | |
319 | consistent OO interface to these files, regardless of how they're | |
426affbf LS |
320 | stored. Databases may be text, dbm, Berkeley DB or any database with |
321 | a DBI compatible driver. HTTPD::UserAdmin supports files used by the | |
68dc0745 | 322 | `Basic' and `Digest' authentication schemes. Here's an example: |
323 | ||
324 | use HTTPD::UserAdmin (); | |
325 | HTTPD::UserAdmin | |
326 | ->new(DB => "/foo/.htpasswd") | |
327 | ->add($username => $password); | |
328 | ||
46fc3d4c | 329 | =head2 How do I make sure users can't enter values into a form that cause my CGI script to do bad things? |
330 | ||
24f1ba9b | 331 | See the security references listed in the CGI Meta FAQ |
46fc3d4c | 332 | |
24f1ba9b | 333 | http://www.perl.org/CGI_MetaFAQ.html |
46fc3d4c | 334 | |
5a964f20 | 335 | =head2 How do I parse a mail header? |
68dc0745 | 336 | |
337 | For a quick-and-dirty solution, try this solution derived | |
b73a15ae | 338 | from L<perlfunc/split>: |
68dc0745 | 339 | |
340 | $/ = ''; | |
341 | $header = <MSG>; | |
342 | $header =~ s/\n\s+/ /g; # merge continuation lines | |
343 | %head = ( UNIX_FROM_LINE, split /^([-\w]+):\s*/m, $header ); | |
344 | ||
345 | That solution doesn't do well if, for example, you're trying to | |
346 | maintain all the Received lines. A more complete approach is to use | |
347 | the Mail::Header module from CPAN (part of the MailTools package). | |
348 | ||
349 | =head2 How do I decode a CGI form? | |
350 | ||
c8db1d39 TC |
351 | You use a standard module, probably CGI.pm. Under no circumstances |
352 | should you attempt to do so by hand! | |
353 | ||
354 | You'll see a lot of CGI programs that blindly read from STDIN the number | |
355 | of bytes equal to CONTENT_LENGTH for POSTs, or grab QUERY_STRING for | |
356 | decoding GETs. These programs are very poorly written. They only work | |
357 | sometimes. They typically forget to check the return value of the read() | |
358 | system call, which is a cardinal sin. They don't handle HEAD requests. | |
359 | They don't handle multipart forms used for file uploads. They don't deal | |
360 | with GET/POST combinations where query fields are in more than one place. | |
361 | They don't deal with keywords in the query string. | |
362 | ||
363 | In short, they're bad hacks. Resist them at all costs. Please do not be | |
364 | tempted to reinvent the wheel. Instead, use the CGI.pm or CGI_Lite.pm | |
365 | (available from CPAN), or if you're trapped in the module-free land | |
366 | of perl1 .. perl4, you might look into cgi-lib.pl (available from | |
65acb1b1 | 367 | http://cgi-lib.stanford.edu/cgi-lib/ ). |
c8db1d39 TC |
368 | |
369 | Make sure you know whether to use a GET or a POST in your form. | |
370 | GETs should only be used for something that doesn't update the server. | |
371 | Otherwise you can get mangled databases and repeated feedback mail | |
372 | messages. The fancy word for this is ``idempotency''. This simply | |
373 | means that there should be no difference between making a GET request | |
374 | for a particular URL once or multiple times. This is because the | |
375 | HTTP protocol definition says that a GET request may be cached by the | |
376 | browser, or server, or an intervening proxy. POST requests cannot be | |
377 | cached, because each request is independent and matters. Typically, | |
378 | POST requests change or depend on state on the server (query or update | |
379 | a database, send mail, or purchase a computer). | |
68dc0745 | 380 | |
5a964f20 | 381 | =head2 How do I check a valid mail address? |
68dc0745 | 382 | |
c8db1d39 | 383 | You can't, at least, not in real time. Bummer, eh? |
68dc0745 | 384 | |
c8db1d39 TC |
385 | Without sending mail to the address and seeing whether there's a human |
386 | on the other hand to answer you, you cannot determine whether a mail | |
387 | address is valid. Even if you apply the mail header standard, you | |
388 | can have problems, because there are deliverable addresses that aren't | |
389 | RFC-822 (the mail header standard) compliant, and addresses that aren't | |
390 | deliverable which are compliant. | |
68dc0745 | 391 | |
49d635f9 RGS |
392 | You can use the Email::Valid or RFC::RFC822::Address which check |
393 | the format of the address, although they cannot actually tell you | |
394 | if it is a deliverable address (i.e. that mail to the address | |
395 | will not bounce). Modules like Mail::CheckUser and Mail::EXPN | |
396 | try to interact with the domain name system or particular | |
397 | mail servers to learn even more, but their methods do not | |
398 | work everywhere---especially for security conscious administrators. | |
399 | ||
c8db1d39 | 400 | Many are tempted to try to eliminate many frequently-invalid |
d92eb7b0 | 401 | mail addresses with a simple regex, such as |
b8c8cfe2 | 402 | C</^[\w.-]+\@(?:[\w-]+\.)+\w+$/>. It's a very bad idea. However, |
c8db1d39 | 403 | this also throws out many valid ones, and says nothing about |
b8c8cfe2 | 404 | potential deliverability, so it is not suggested. Instead, see |
1577cd80 | 405 | http://www.cpan.org/authors/Tom_Christiansen/scripts/ckaddr.gz , |
68dc0745 | 406 | which actually checks against the full RFC spec (except for nested |
5a964f20 | 407 | comments), looks for addresses you may not wish to accept mail to |
68dc0745 | 408 | (say, Bill Clinton or your postmaster), and then makes sure that the |
c8db1d39 TC |
409 | hostname given can be looked up in the DNS MX records. It's not fast, |
410 | but it works for what it tries to do. | |
411 | ||
412 | Our best advice for verifying a person's mail address is to have them | |
413 | enter their address twice, just as you normally do to change a password. | |
414 | This usually weeds out typos. If both versions match, send | |
415 | mail to that address with a personal message that looks somewhat like: | |
416 | ||
417 | Dear someuser@host.com, | |
418 | ||
419 | Please confirm the mail address you gave us Wed May 6 09:38:41 | |
420 | MDT 1998 by replying to this message. Include the string | |
421 | "Rumpelstiltskin" in that reply, but spelled in reverse; that is, | |
422 | start with "Nik...". Once this is done, your confirmed address will | |
423 | be entered into our records. | |
424 | ||
425 | If you get the message back and they've followed your directions, | |
426 | you can be reasonably assured that it's real. | |
68dc0745 | 427 | |
c8db1d39 TC |
428 | A related strategy that's less open to forgery is to give them a PIN |
429 | (personal ID number). Record the address and PIN (best that it be a | |
430 | random one) for later processing. In the mail you send, ask them to | |
431 | include the PIN in their reply. But if it bounces, or the message is | |
432 | included via a ``vacation'' script, it'll be there anyway. So it's | |
433 | best to ask them to mail back a slight alteration of the PIN, such as | |
434 | with the characters reversed, one added or subtracted to each digit, etc. | |
46fc3d4c | 435 | |
68dc0745 | 436 | =head2 How do I decode a MIME/BASE64 string? |
437 | ||
6a0af2f1 GA |
438 | The MIME-Base64 package (available from CPAN) handles this as well as |
439 | the MIME/QP encoding. Decoding BASE64 becomes as simple as: | |
68dc0745 | 440 | |
6a0af2f1 | 441 | use MIME::Base64; |
68dc0745 | 442 | $decoded = decode_base64($encoded); |
443 | ||
26d9b02f | 444 | The MIME-Tools package (available from CPAN) supports extraction with |
6a0af2f1 GA |
445 | decoding of BASE64 encoded attachments and content directly from email |
446 | messages. | |
447 | ||
448 | If the string to decode is short (less than 84 bytes long) | |
449 | a more direct approach is to use the unpack() function's "u" | |
68dc0745 | 450 | format after minor transliterations: |
451 | ||
452 | tr#A-Za-z0-9+/##cd; # remove non-base64 chars | |
453 | tr#A-Za-z0-9+/# -_#; # convert to uuencoded format | |
454 | $len = pack("c", 32 + 0.75*length); # compute length byte | |
455 | print unpack("u", $len . $_); # uudecode and print | |
456 | ||
5a964f20 | 457 | =head2 How do I return the user's mail address? |
68dc0745 | 458 | |
a6dd486b | 459 | On systems that support getpwuid, the $< variable, and the |
68dc0745 | 460 | Sys::Hostname module (which is part of the standard perl distribution), |
461 | you can probably try using something like this: | |
462 | ||
463 | use Sys::Hostname; | |
231ab6d1 | 464 | $address = sprintf('%s@%s', scalar getpwuid($<), hostname); |
68dc0745 | 465 | |
5a964f20 TC |
466 | Company policies on mail address can mean that this generates addresses |
467 | that the company's mail system will not accept, so you should ask for | |
468 | users' mail addresses when this matters. Furthermore, not all systems | |
68dc0745 | 469 | on which Perl runs are so forthcoming with this information as is Unix. |
470 | ||
471 | The Mail::Util module from CPAN (part of the MailTools package) provides a | |
472 | mailaddress() function that tries to guess the mail address of the user. | |
473 | It makes a more intelligent guess than the code above, using information | |
474 | given when the module was installed, but it could still be incorrect. | |
475 | Again, the best way is often just to ask the user. | |
476 | ||
c8db1d39 | 477 | =head2 How do I send mail? |
68dc0745 | 478 | |
c8db1d39 TC |
479 | Use the C<sendmail> program directly: |
480 | ||
481 | open(SENDMAIL, "|/usr/lib/sendmail -oi -t -odq") | |
482 | or die "Can't fork for sendmail: $!\n"; | |
483 | print SENDMAIL <<"EOF"; | |
484 | From: User Originating Mail <me\@host> | |
485 | To: Final Destination <you\@otherhost> | |
486 | Subject: A relevant subject line | |
487 | ||
65acb1b1 TC |
488 | Body of the message goes here after the blank line |
489 | in as many lines as you like. | |
c8db1d39 TC |
490 | EOF |
491 | close(SENDMAIL) or warn "sendmail didn't close nicely"; | |
492 | ||
493 | The B<-oi> option prevents sendmail from interpreting a line consisting | |
494 | of a single dot as "end of message". The B<-t> option says to use the | |
495 | headers to decide who to send the message to, and B<-odq> says to put | |
496 | the message into the queue. This last option means your message won't | |
497 | be immediately delivered, so leave it out if you want immediate | |
498 | delivery. | |
499 | ||
d92eb7b0 GS |
500 | Alternate, less convenient approaches include calling mail (sometimes |
501 | called mailx) directly or simply opening up port 25 have having an | |
502 | intimate conversation between just you and the remote SMTP daemon, | |
503 | probably sendmail. | |
504 | ||
505 | Or you might be able use the CPAN module Mail::Mailer: | |
c8db1d39 TC |
506 | |
507 | use Mail::Mailer; | |
508 | ||
509 | $mailer = Mail::Mailer->new(); | |
510 | $mailer->open({ From => $from_address, | |
511 | To => $to_address, | |
512 | Subject => $subject, | |
513 | }) | |
514 | or die "Can't open: $!\n"; | |
515 | print $mailer $body; | |
516 | $mailer->close(); | |
517 | ||
518 | The Mail::Internet module uses Net::SMTP which is less Unix-centric than | |
519 | Mail::Mailer, but less reliable. Avoid raw SMTP commands. There | |
d92eb7b0 | 520 | are many reasons to use a mail transport agent like sendmail. These |
8305e449 | 521 | include queuing, MX records, and security. |
c8db1d39 | 522 | |
575cc754 JH |
523 | =head2 How do I use MIME to make an attachment to a mail message? |
524 | ||
525 | This answer is extracted directly from the MIME::Lite documentation. | |
526 | Create a multipart message (i.e., one with attachments). | |
527 | ||
528 | use MIME::Lite; | |
529 | ||
530 | ### Create a new multipart message: | |
531 | $msg = MIME::Lite->new( | |
532 | From =>'me@myhost.com', | |
533 | To =>'you@yourhost.com', | |
534 | Cc =>'some@other.com, some@more.com', | |
535 | Subject =>'A message with 2 parts...', | |
536 | Type =>'multipart/mixed' | |
537 | ); | |
538 | ||
539 | ### Add parts (each "attach" has same arguments as "new"): | |
540 | $msg->attach(Type =>'TEXT', | |
541 | Data =>"Here's the GIF file you wanted" | |
542 | ); | |
543 | $msg->attach(Type =>'image/gif', | |
544 | Path =>'aaa000123.gif', | |
545 | Filename =>'logo.gif' | |
546 | ); | |
547 | ||
548 | $text = $msg->as_string; | |
549 | ||
550 | MIME::Lite also includes a method for sending these things. | |
551 | ||
552 | $msg->send; | |
553 | ||
197aec24 | 554 | This defaults to using L<sendmail> but can be customized to use |
575cc754 JH |
555 | SMTP via L<Net::SMTP>. |
556 | ||
c8db1d39 TC |
557 | =head2 How do I read mail? |
558 | ||
d92eb7b0 | 559 | While you could use the Mail::Folder module from CPAN (part of the |
5cd0b561 | 560 | MailFolder package) or the Mail::Internet module from CPAN (part |
a6dd486b | 561 | of the MailTools package), often a module is overkill. Here's a |
d92eb7b0 GS |
562 | mail sorter. |
563 | ||
564 | #!/usr/bin/perl | |
5cd0b561 | 565 | |
c8db1d39 TC |
566 | my(@msgs, @sub); |
567 | my $msgno = -1; | |
568 | $/ = ''; # paragraph reads | |
569 | while (<>) { | |
5cd0b561 | 570 | if (/^From /m) { |
c8db1d39 TC |
571 | /^Subject:\s*(?:Re:\s*)*(.*)/mi; |
572 | $sub[++$msgno] = lc($1) || ''; | |
573 | } | |
574 | $msgs[$msgno] .= $_; | |
d92eb7b0 | 575 | } |
c8db1d39 TC |
576 | for my $i (sort { $sub[$a] cmp $sub[$b] || $a <=> $b } (0 .. $#msgs)) { |
577 | print $msgs[$i]; | |
578 | } | |
579 | ||
d92eb7b0 | 580 | Or more succinctly, |
c8db1d39 TC |
581 | |
582 | #!/usr/bin/perl -n00 | |
583 | # bysub2 - awkish sort-by-subject | |
584 | BEGIN { $msgno = -1 } | |
585 | $sub[++$msgno] = (/^Subject:\s*(?:Re:\s*)*(.*)/mi)[0] if /^From/m; | |
586 | $msg[$msgno] .= $_; | |
587 | END { print @msg[ sort { $sub[$a] cmp $sub[$b] || $a <=> $b } (0 .. $#msg) ] } | |
588 | ||
68dc0745 | 589 | =head2 How do I find out my hostname/domainname/IP address? |
590 | ||
c8db1d39 TC |
591 | The normal way to find your own hostname is to call the C<`hostname`> |
592 | program. While sometimes expedient, this has some problems, such as | |
593 | not knowing whether you've got the canonical name or not. It's one of | |
594 | those tradeoffs of convenience versus portability. | |
68dc0745 | 595 | |
596 | The Sys::Hostname module (part of the standard perl distribution) will | |
597 | give you the hostname after which you can find out the IP address | |
598 | (assuming you have working DNS) with a gethostbyname() call. | |
599 | ||
600 | use Socket; | |
601 | use Sys::Hostname; | |
602 | my $host = hostname(); | |
65acb1b1 | 603 | my $addr = inet_ntoa(scalar gethostbyname($host || 'localhost')); |
68dc0745 | 604 | |
605 | Probably the simplest way to learn your DNS domain name is to grok | |
606 | it out of /etc/resolv.conf, at least under Unix. Of course, this | |
607 | assumes several things about your resolv.conf configuration, including | |
608 | that it exists. | |
609 | ||
610 | (We still need a good DNS domain name-learning method for non-Unix | |
611 | systems.) | |
612 | ||
613 | =head2 How do I fetch a news article or the active newsgroups? | |
614 | ||
615 | Use the Net::NNTP or News::NNTPClient modules, both available from CPAN. | |
a6dd486b | 616 | This can make tasks like fetching the newsgroup list as simple as |
68dc0745 | 617 | |
618 | perl -MNews::NNTPClient | |
619 | -e 'print News::NNTPClient->new->list("newsgroups")' | |
620 | ||
621 | =head2 How do I fetch/put an FTP file? | |
622 | ||
623 | LWP::Simple (available from CPAN) can fetch but not put. Net::FTP (also | |
624 | available from CPAN) is more complex but can put as well as fetch. | |
625 | ||
626 | =head2 How can I do RPC in Perl? | |
627 | ||
a6dd486b | 628 | A DCE::RPC module is being developed (but is not yet available) and |
68dc0745 | 629 | will be released as part of the DCE-Perl package (available from |
65acb1b1 TC |
630 | CPAN). The rpcgen suite, available from CPAN/authors/id/JAKE/, is |
631 | an RPC stub generator and includes an RPC::ONC module. | |
68dc0745 | 632 | |
633 | =head1 AUTHOR AND COPYRIGHT | |
634 | ||
0bc0ad85 | 635 | Copyright (c) 1997-2002 Tom Christiansen and Nathan Torkington. |
5a964f20 TC |
636 | All rights reserved. |
637 | ||
5a7beb56 JH |
638 | This documentation is free; you can redistribute it and/or modify it |
639 | under the same terms as Perl itself. | |
5a964f20 TC |
640 | |
641 | Irrespective of its distribution, all code examples in this file | |
642 | are hereby placed into the public domain. You are permitted and | |
643 | encouraged to use this code in your own programs for fun | |
644 | or for profit as you see fit. A simple comment in the code giving | |
645 | credit would be courteous but is not required. |