Commit | Line | Data |
68dc0745 |
1 | =head1 NAME |
2 | |
213329dd |
3 | perlfaq9 - Networking ($Revision: 1.5 $, $Date: 2001/11/09 08:06:04 $) |
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 |
12 | (Alan Flavell <flavell+www@a5.ph.gla.ac.uk> answers...) |
13 | |
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 |
18 | |
19 | The original CGI specification is at: http://hoohoo.ncsa.uiuc.edu/cgi/ |
20 | |
21 | Current best-practice RFC draft at: http://CGI-Spec.Golux.Com/ |
22 | |
23 | Other relevant documentation listed in: http://www.perl.org/CGI_MetaFAQ.html |
68dc0745 |
24 | |
24f1ba9b |
25 | These Perl FAQs very selectively cover some CGI issues. However, Perl |
26 | programmers are strongly advised to use the CGI.pm module, to take care |
27 | of the details for them. |
68dc0745 |
28 | |
24f1ba9b |
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 |
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 |
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 | |
24f1ba9b |
51 | If you can demonstrate that you've read the FAQs and that |
52 | your problem isn't something simple that can be easily answered, you'll |
53 | probably receive a courteous and useful reply to your question if you |
54 | post it on comp.infosystems.www.authoring.cgi (if it's something to do |
55 | with HTTP or the CGI protocols). Questions that appear to be Perl |
56 | questions but are really CGI ones that are posted to comp.lang.perl.misc |
57 | are not so well received. |
c8db1d39 |
58 | |
24f1ba9b |
59 | The useful FAQs, related documents, and troubleshooting guides are |
60 | listed in the CGI Meta FAQ: |
61 | |
62 | http://www.perl.org/CGI_MetaFAQ.html |
c8db1d39 |
63 | |
c8db1d39 |
64 | |
65 | =head2 How can I get better error messages from a CGI program? |
66 | |
67 | Use the CGI::Carp module. It replaces C<warn> and C<die>, plus the |
68 | normal Carp modules C<carp>, C<croak>, and C<confess> functions with |
69 | more verbose and safer versions. It still sends them to the normal |
70 | server error log. |
71 | |
72 | use CGI::Carp; |
73 | warn "This is a complaint"; |
74 | die "But this one is serious"; |
75 | |
76 | The following use of CGI::Carp also redirects errors to a file of your choice, |
77 | placed in a BEGIN block to catch compile-time warnings as well: |
78 | |
79 | BEGIN { |
80 | use CGI::Carp qw(carpout); |
81 | open(LOG, ">>/var/local/cgi-logs/mycgi-log") |
82 | or die "Unable to append to mycgi-log: $!\n"; |
83 | carpout(*LOG); |
84 | } |
85 | |
86 | You can even arrange for fatal errors to go back to the client browser, |
87 | which is nice for your own debugging, but might confuse the end user. |
88 | |
89 | use CGI::Carp qw(fatalsToBrowser); |
90 | die "Bad error here"; |
91 | |
92 | Even if the error happens before you get the HTTP header out, the module |
93 | will try to take care of this to avoid the dreaded server 500 errors. |
94 | Normal warnings still go out to the server error log (or wherever |
95 | you've sent them with C<carpout>) with the application name and date |
96 | stamp prepended. |
97 | |
68dc0745 |
98 | =head2 How do I remove HTML from a string? |
99 | |
f29c64d6 |
100 | The most correct way (albeit not the fastest) is to use HTML::Parser |
bed171df |
101 | from CPAN. Another mostly correct |
7d7e76cf |
102 | way is to use HTML::FormatText which not only removes HTML but also |
103 | attempts to do a little simple formatting of the resulting plain text. |
68dc0745 |
104 | |
105 | Many folks attempt a simple-minded regular expression approach, like |
c47ff5f1 |
106 | C<< s/<.*?>//g >>, but that fails in many cases because the tags |
68dc0745 |
107 | may continue over line breaks, they may contain quoted angle-brackets, |
a6dd486b |
108 | or HTML comment may be present. Plus, folks forget to convert |
109 | entities--like C<<> for example. |
68dc0745 |
110 | |
111 | Here's one "simple-minded" approach, that works for most files: |
112 | |
113 | #!/usr/bin/perl -p0777 |
114 | s/<(?:[^>'"]*|(['"]).*?\1)*>//gs |
115 | |
116 | If you want a more complete solution, see the 3-stage striphtml |
117 | program in |
a93751fa |
118 | http://www.cpan.org/authors/Tom_Christiansen/scripts/striphtml.gz |
68dc0745 |
119 | . |
120 | |
c8db1d39 |
121 | Here are some tricky cases that you should think about when picking |
122 | a solution: |
123 | |
124 | <IMG SRC = "foo.gif" ALT = "A > B"> |
125 | |
d92eb7b0 |
126 | <IMG SRC = "foo.gif" |
c8db1d39 |
127 | ALT = "A > B"> |
128 | |
129 | <!-- <A comment> --> |
130 | |
131 | <script>if (a<b && a>c)</script> |
132 | |
133 | <# Just data #> |
134 | |
135 | <![INCLUDE CDATA [ >>>>>>>>>>>> ]]> |
136 | |
137 | If HTML comments include other tags, those solutions would also break |
138 | on text like this: |
139 | |
140 | <!-- This section commented out. |
141 | <B>You can't see me!</B> |
142 | --> |
143 | |
68dc0745 |
144 | =head2 How do I extract URLs? |
145 | |
e67d034e |
146 | You can easily extract all sorts of URLs from HTML with |
147 | C<HTML::SimpleLinkExtor> which handles anchors, images, objects, |
148 | frames, and many other tags that can contain a URL. If you need |
149 | anything more complex, you can create your own subclass of |
150 | C<HTML::LinkExtor> or C<HTML::Parser>. You might even use |
151 | C<HTML::SimpleLinkExtor> as an example for something specifically |
152 | suited to your needs. |
153 | |
154 | Less complete solutions involving regular expressions can save |
155 | you a lot of processing time if you know that the input is simple. One |
156 | solution from Tom Christiansen runs 100 times faster than most |
157 | module based approaches but only extracts URLs from anchors where the first |
158 | attribute is HREF and there are no other attributes. |
159 | |
160 | #!/usr/bin/perl -n00 |
161 | # qxurl - tchrist@perl.com |
162 | print "$2\n" while m{ |
163 | < \s* |
164 | A \s+ HREF \s* = \s* (["']) (.*?) \1 |
165 | \s* > |
166 | }gsix; |
167 | |
68dc0745 |
168 | |
169 | =head2 How do I download a file from the user's machine? How do I open a file on another machine? |
170 | |
171 | In the context of an HTML form, you can use what's known as |
172 | B<multipart/form-data> encoding. The CGI.pm module (available from |
173 | CPAN) supports this in the start_multipart_form() method, which isn't |
174 | the same as the startform() method. |
175 | |
176 | =head2 How do I make a pop-up menu in HTML? |
177 | |
c47ff5f1 |
178 | Use the B<< <SELECT> >> and B<< <OPTION> >> tags. The CGI.pm |
68dc0745 |
179 | module (available from CPAN) supports this widget, as well as many |
180 | others, including some that it cleverly synthesizes on its own. |
181 | |
182 | =head2 How do I fetch an HTML file? |
183 | |
46fc3d4c |
184 | One approach, if you have the lynx text-based HTML browser installed |
185 | on your system, is this: |
68dc0745 |
186 | |
187 | $html_code = `lynx -source $url`; |
188 | $text_data = `lynx -dump $url`; |
189 | |
d92eb7b0 |
190 | The libwww-perl (LWP) modules from CPAN provide a more powerful way |
191 | to do this. They don't require lynx, but like lynx, can still work |
192 | through proxies: |
46fc3d4c |
193 | |
c8db1d39 |
194 | # simplest version |
195 | use LWP::Simple; |
196 | $content = get($URL); |
197 | |
198 | # or print HTML from a URL |
46fc3d4c |
199 | use LWP::Simple; |
6cecdcac |
200 | getprint "http://www.linpro.no/lwp/"; |
46fc3d4c |
201 | |
c8db1d39 |
202 | # or print ASCII from HTML from a URL |
65acb1b1 |
203 | # also need HTML-Tree package from CPAN |
46fc3d4c |
204 | use LWP::Simple; |
f29c64d6 |
205 | use HTML::Parser; |
46fc3d4c |
206 | use HTML::FormatText; |
207 | my ($html, $ascii); |
208 | $html = get("http://www.perl.com/"); |
209 | defined $html |
210 | or die "Can't fetch HTML from http://www.perl.com/"; |
211 | $ascii = HTML::FormatText->new->format(parse_html($html)); |
212 | print $ascii; |
213 | |
c8db1d39 |
214 | =head2 How do I automate an HTML form submission? |
215 | |
216 | If you're submitting values using the GET method, create a URL and encode |
217 | the form using the C<query_form> method: |
218 | |
219 | use LWP::Simple; |
220 | use URI::URL; |
221 | |
222 | my $url = url('http://www.perl.com/cgi-bin/cpan_mod'); |
223 | $url->query_form(module => 'DB_File', readme => 1); |
224 | $content = get($url); |
225 | |
226 | If you're using the POST method, create your own user agent and encode |
227 | the content appropriately. |
228 | |
229 | use HTTP::Request::Common qw(POST); |
230 | use LWP::UserAgent; |
231 | |
232 | $ua = LWP::UserAgent->new(); |
233 | my $req = POST 'http://www.perl.com/cgi-bin/cpan_mod', |
234 | [ module => 'DB_File', readme => 1 ]; |
235 | $content = $ua->request($req)->as_string; |
236 | |
237 | =head2 How do I decode or create those %-encodings on the web? |
68dc0745 |
238 | |
68dc0745 |
239 | |
575cc754 |
240 | If you are writing a CGI script, you should be using the CGI.pm module |
241 | that comes with perl, or some other equivalent module. The CGI module |
242 | automatically decodes queries for you, and provides an escape() |
243 | function to handle encoding. |
68dc0745 |
244 | |
575cc754 |
245 | |
246 | The best source of detailed information on URI encoding is RFC 2396. |
247 | Basically, the following substitutions do it: |
248 | |
249 | s/([^\w()'*~!.-])/sprintf '%%%02x', $1/eg; # encode |
250 | |
251 | s/%([A-Fa-f\d]{2})/chr hex $1/eg; # decode |
252 | |
253 | However, you should only apply them to individual URI components, not |
254 | the entire URI, otherwise you'll lose information and generally mess |
255 | things up. If that didn't explain it, don't worry. Just go read |
256 | section 2 of the RFC, it's probably the best explanation there is. |
257 | |
258 | RFC 2396 also contains a lot of other useful information, including a |
259 | regexp for breaking any arbitrary URI into components (Appendix B). |
68dc0745 |
260 | |
261 | =head2 How do I redirect to another page? |
262 | |
24f1ba9b |
263 | Specify the complete URL of the destination (even if it is on the same |
264 | server). This is one of the two different kinds of CGI "Location:" |
265 | responses which are defined in the CGI specification for a Parsed Headers |
266 | script. The other kind (an absolute URLpath) is resolved internally to |
267 | the server without any HTTP redirection. The CGI specifications do not |
268 | allow relative URLs in either case. |
269 | |
270 | Use of CGI.pm is strongly recommended. This example shows redirection |
271 | with a complete URL. This redirection is handled by the web browser. |
272 | |
273 | use CGI qw/:standard/; |
274 | |
a93751fa |
275 | my $url = 'http://www.cpan.org/'; |
24f1ba9b |
276 | print redirect($url); |
68dc0745 |
277 | |
68dc0745 |
278 | |
24f1ba9b |
279 | This example shows a redirection with an absolute URLpath. This |
280 | redirection is handled by the local web server. |
68dc0745 |
281 | |
24f1ba9b |
282 | my $url = '/CPAN/index.html'; |
283 | print redirect($url); |
c8db1d39 |
284 | |
d92eb7b0 |
285 | |
24f1ba9b |
286 | But if coded directly, it could be as follows (the final "\n" is |
287 | shown separately, for clarity), using either a complete URL or |
288 | an absolute URLpath. |
d92eb7b0 |
289 | |
24f1ba9b |
290 | print "Location: $url\n"; # CGI response header |
291 | print "\n"; # end of headers |
d92eb7b0 |
292 | |
c8db1d39 |
293 | |
68dc0745 |
294 | =head2 How do I put a password on my web pages? |
295 | |
296 | That depends. You'll need to read the documentation for your web |
297 | server, or perhaps check some of the other FAQs referenced above. |
298 | |
299 | =head2 How do I edit my .htpasswd and .htgroup files with Perl? |
300 | |
301 | The HTTPD::UserAdmin and HTTPD::GroupAdmin modules provide a |
302 | consistent OO interface to these files, regardless of how they're |
426affbf |
303 | stored. Databases may be text, dbm, Berkeley DB or any database with |
304 | a DBI compatible driver. HTTPD::UserAdmin supports files used by the |
68dc0745 |
305 | `Basic' and `Digest' authentication schemes. Here's an example: |
306 | |
307 | use HTTPD::UserAdmin (); |
308 | HTTPD::UserAdmin |
309 | ->new(DB => "/foo/.htpasswd") |
310 | ->add($username => $password); |
311 | |
46fc3d4c |
312 | =head2 How do I make sure users can't enter values into a form that cause my CGI script to do bad things? |
313 | |
24f1ba9b |
314 | See the security references listed in the CGI Meta FAQ |
46fc3d4c |
315 | |
24f1ba9b |
316 | http://www.perl.org/CGI_MetaFAQ.html |
46fc3d4c |
317 | |
5a964f20 |
318 | =head2 How do I parse a mail header? |
68dc0745 |
319 | |
320 | For a quick-and-dirty solution, try this solution derived |
b73a15ae |
321 | from L<perlfunc/split>: |
68dc0745 |
322 | |
323 | $/ = ''; |
324 | $header = <MSG>; |
325 | $header =~ s/\n\s+/ /g; # merge continuation lines |
326 | %head = ( UNIX_FROM_LINE, split /^([-\w]+):\s*/m, $header ); |
327 | |
328 | That solution doesn't do well if, for example, you're trying to |
329 | maintain all the Received lines. A more complete approach is to use |
330 | the Mail::Header module from CPAN (part of the MailTools package). |
331 | |
332 | =head2 How do I decode a CGI form? |
333 | |
c8db1d39 |
334 | You use a standard module, probably CGI.pm. Under no circumstances |
335 | should you attempt to do so by hand! |
336 | |
337 | You'll see a lot of CGI programs that blindly read from STDIN the number |
338 | of bytes equal to CONTENT_LENGTH for POSTs, or grab QUERY_STRING for |
339 | decoding GETs. These programs are very poorly written. They only work |
340 | sometimes. They typically forget to check the return value of the read() |
341 | system call, which is a cardinal sin. They don't handle HEAD requests. |
342 | They don't handle multipart forms used for file uploads. They don't deal |
343 | with GET/POST combinations where query fields are in more than one place. |
344 | They don't deal with keywords in the query string. |
345 | |
346 | In short, they're bad hacks. Resist them at all costs. Please do not be |
347 | tempted to reinvent the wheel. Instead, use the CGI.pm or CGI_Lite.pm |
348 | (available from CPAN), or if you're trapped in the module-free land |
349 | of perl1 .. perl4, you might look into cgi-lib.pl (available from |
65acb1b1 |
350 | http://cgi-lib.stanford.edu/cgi-lib/ ). |
c8db1d39 |
351 | |
352 | Make sure you know whether to use a GET or a POST in your form. |
353 | GETs should only be used for something that doesn't update the server. |
354 | Otherwise you can get mangled databases and repeated feedback mail |
355 | messages. The fancy word for this is ``idempotency''. This simply |
356 | means that there should be no difference between making a GET request |
357 | for a particular URL once or multiple times. This is because the |
358 | HTTP protocol definition says that a GET request may be cached by the |
359 | browser, or server, or an intervening proxy. POST requests cannot be |
360 | cached, because each request is independent and matters. Typically, |
361 | POST requests change or depend on state on the server (query or update |
362 | a database, send mail, or purchase a computer). |
68dc0745 |
363 | |
5a964f20 |
364 | =head2 How do I check a valid mail address? |
68dc0745 |
365 | |
c8db1d39 |
366 | You can't, at least, not in real time. Bummer, eh? |
68dc0745 |
367 | |
c8db1d39 |
368 | Without sending mail to the address and seeing whether there's a human |
369 | on the other hand to answer you, you cannot determine whether a mail |
370 | address is valid. Even if you apply the mail header standard, you |
371 | can have problems, because there are deliverable addresses that aren't |
372 | RFC-822 (the mail header standard) compliant, and addresses that aren't |
373 | deliverable which are compliant. |
68dc0745 |
374 | |
c8db1d39 |
375 | Many are tempted to try to eliminate many frequently-invalid |
d92eb7b0 |
376 | mail addresses with a simple regex, such as |
b8c8cfe2 |
377 | C</^[\w.-]+\@(?:[\w-]+\.)+\w+$/>. It's a very bad idea. However, |
c8db1d39 |
378 | this also throws out many valid ones, and says nothing about |
b8c8cfe2 |
379 | potential deliverability, so it is not suggested. Instead, see |
a93751fa |
380 | http://www.cpan.org/authors/Tom_Christiansen/scripts/ckaddr.gz, |
68dc0745 |
381 | which actually checks against the full RFC spec (except for nested |
5a964f20 |
382 | comments), looks for addresses you may not wish to accept mail to |
68dc0745 |
383 | (say, Bill Clinton or your postmaster), and then makes sure that the |
c8db1d39 |
384 | hostname given can be looked up in the DNS MX records. It's not fast, |
385 | but it works for what it tries to do. |
386 | |
387 | Our best advice for verifying a person's mail address is to have them |
388 | enter their address twice, just as you normally do to change a password. |
389 | This usually weeds out typos. If both versions match, send |
390 | mail to that address with a personal message that looks somewhat like: |
391 | |
392 | Dear someuser@host.com, |
393 | |
394 | Please confirm the mail address you gave us Wed May 6 09:38:41 |
395 | MDT 1998 by replying to this message. Include the string |
396 | "Rumpelstiltskin" in that reply, but spelled in reverse; that is, |
397 | start with "Nik...". Once this is done, your confirmed address will |
398 | be entered into our records. |
399 | |
400 | If you get the message back and they've followed your directions, |
401 | you can be reasonably assured that it's real. |
68dc0745 |
402 | |
c8db1d39 |
403 | A related strategy that's less open to forgery is to give them a PIN |
404 | (personal ID number). Record the address and PIN (best that it be a |
405 | random one) for later processing. In the mail you send, ask them to |
406 | include the PIN in their reply. But if it bounces, or the message is |
407 | included via a ``vacation'' script, it'll be there anyway. So it's |
408 | best to ask them to mail back a slight alteration of the PIN, such as |
409 | with the characters reversed, one added or subtracted to each digit, etc. |
46fc3d4c |
410 | |
68dc0745 |
411 | =head2 How do I decode a MIME/BASE64 string? |
412 | |
6a0af2f1 |
413 | The MIME-Base64 package (available from CPAN) handles this as well as |
414 | the MIME/QP encoding. Decoding BASE64 becomes as simple as: |
68dc0745 |
415 | |
6a0af2f1 |
416 | use MIME::Base64; |
68dc0745 |
417 | $decoded = decode_base64($encoded); |
418 | |
26d9b02f |
419 | The MIME-Tools package (available from CPAN) supports extraction with |
6a0af2f1 |
420 | decoding of BASE64 encoded attachments and content directly from email |
421 | messages. |
422 | |
423 | If the string to decode is short (less than 84 bytes long) |
424 | a more direct approach is to use the unpack() function's "u" |
68dc0745 |
425 | format after minor transliterations: |
426 | |
427 | tr#A-Za-z0-9+/##cd; # remove non-base64 chars |
428 | tr#A-Za-z0-9+/# -_#; # convert to uuencoded format |
429 | $len = pack("c", 32 + 0.75*length); # compute length byte |
430 | print unpack("u", $len . $_); # uudecode and print |
431 | |
5a964f20 |
432 | =head2 How do I return the user's mail address? |
68dc0745 |
433 | |
a6dd486b |
434 | On systems that support getpwuid, the $< variable, and the |
68dc0745 |
435 | Sys::Hostname module (which is part of the standard perl distribution), |
436 | you can probably try using something like this: |
437 | |
438 | use Sys::Hostname; |
231ab6d1 |
439 | $address = sprintf('%s@%s', scalar getpwuid($<), hostname); |
68dc0745 |
440 | |
5a964f20 |
441 | Company policies on mail address can mean that this generates addresses |
442 | that the company's mail system will not accept, so you should ask for |
443 | users' mail addresses when this matters. Furthermore, not all systems |
68dc0745 |
444 | on which Perl runs are so forthcoming with this information as is Unix. |
445 | |
446 | The Mail::Util module from CPAN (part of the MailTools package) provides a |
447 | mailaddress() function that tries to guess the mail address of the user. |
448 | It makes a more intelligent guess than the code above, using information |
449 | given when the module was installed, but it could still be incorrect. |
450 | Again, the best way is often just to ask the user. |
451 | |
c8db1d39 |
452 | =head2 How do I send mail? |
68dc0745 |
453 | |
c8db1d39 |
454 | Use the C<sendmail> program directly: |
455 | |
456 | open(SENDMAIL, "|/usr/lib/sendmail -oi -t -odq") |
457 | or die "Can't fork for sendmail: $!\n"; |
458 | print SENDMAIL <<"EOF"; |
459 | From: User Originating Mail <me\@host> |
460 | To: Final Destination <you\@otherhost> |
461 | Subject: A relevant subject line |
462 | |
65acb1b1 |
463 | Body of the message goes here after the blank line |
464 | in as many lines as you like. |
c8db1d39 |
465 | EOF |
466 | close(SENDMAIL) or warn "sendmail didn't close nicely"; |
467 | |
468 | The B<-oi> option prevents sendmail from interpreting a line consisting |
469 | of a single dot as "end of message". The B<-t> option says to use the |
470 | headers to decide who to send the message to, and B<-odq> says to put |
471 | the message into the queue. This last option means your message won't |
472 | be immediately delivered, so leave it out if you want immediate |
473 | delivery. |
474 | |
d92eb7b0 |
475 | Alternate, less convenient approaches include calling mail (sometimes |
476 | called mailx) directly or simply opening up port 25 have having an |
477 | intimate conversation between just you and the remote SMTP daemon, |
478 | probably sendmail. |
479 | |
480 | Or you might be able use the CPAN module Mail::Mailer: |
c8db1d39 |
481 | |
482 | use Mail::Mailer; |
483 | |
484 | $mailer = Mail::Mailer->new(); |
485 | $mailer->open({ From => $from_address, |
486 | To => $to_address, |
487 | Subject => $subject, |
488 | }) |
489 | or die "Can't open: $!\n"; |
490 | print $mailer $body; |
491 | $mailer->close(); |
492 | |
493 | The Mail::Internet module uses Net::SMTP which is less Unix-centric than |
494 | Mail::Mailer, but less reliable. Avoid raw SMTP commands. There |
d92eb7b0 |
495 | are many reasons to use a mail transport agent like sendmail. These |
8305e449 |
496 | include queuing, MX records, and security. |
c8db1d39 |
497 | |
575cc754 |
498 | =head2 How do I use MIME to make an attachment to a mail message? |
499 | |
500 | This answer is extracted directly from the MIME::Lite documentation. |
501 | Create a multipart message (i.e., one with attachments). |
502 | |
503 | use MIME::Lite; |
504 | |
505 | ### Create a new multipart message: |
506 | $msg = MIME::Lite->new( |
507 | From =>'me@myhost.com', |
508 | To =>'you@yourhost.com', |
509 | Cc =>'some@other.com, some@more.com', |
510 | Subject =>'A message with 2 parts...', |
511 | Type =>'multipart/mixed' |
512 | ); |
513 | |
514 | ### Add parts (each "attach" has same arguments as "new"): |
515 | $msg->attach(Type =>'TEXT', |
516 | Data =>"Here's the GIF file you wanted" |
517 | ); |
518 | $msg->attach(Type =>'image/gif', |
519 | Path =>'aaa000123.gif', |
520 | Filename =>'logo.gif' |
521 | ); |
522 | |
523 | $text = $msg->as_string; |
524 | |
525 | MIME::Lite also includes a method for sending these things. |
526 | |
527 | $msg->send; |
528 | |
529 | This defaults to using L<sendmail(1)> but can be customized to use |
530 | SMTP via L<Net::SMTP>. |
531 | |
c8db1d39 |
532 | =head2 How do I read mail? |
533 | |
d92eb7b0 |
534 | While you could use the Mail::Folder module from CPAN (part of the |
535 | MailFolder package) or the Mail::Internet module from CPAN (also part |
a6dd486b |
536 | of the MailTools package), often a module is overkill. Here's a |
d92eb7b0 |
537 | mail sorter. |
538 | |
539 | #!/usr/bin/perl |
c8db1d39 |
540 | # bysub1 - simple sort by subject |
541 | my(@msgs, @sub); |
542 | my $msgno = -1; |
543 | $/ = ''; # paragraph reads |
544 | while (<>) { |
545 | if (/^From/m) { |
546 | /^Subject:\s*(?:Re:\s*)*(.*)/mi; |
547 | $sub[++$msgno] = lc($1) || ''; |
548 | } |
549 | $msgs[$msgno] .= $_; |
d92eb7b0 |
550 | } |
c8db1d39 |
551 | for my $i (sort { $sub[$a] cmp $sub[$b] || $a <=> $b } (0 .. $#msgs)) { |
552 | print $msgs[$i]; |
553 | } |
554 | |
d92eb7b0 |
555 | Or more succinctly, |
c8db1d39 |
556 | |
557 | #!/usr/bin/perl -n00 |
558 | # bysub2 - awkish sort-by-subject |
559 | BEGIN { $msgno = -1 } |
560 | $sub[++$msgno] = (/^Subject:\s*(?:Re:\s*)*(.*)/mi)[0] if /^From/m; |
561 | $msg[$msgno] .= $_; |
562 | END { print @msg[ sort { $sub[$a] cmp $sub[$b] || $a <=> $b } (0 .. $#msg) ] } |
563 | |
68dc0745 |
564 | =head2 How do I find out my hostname/domainname/IP address? |
565 | |
c8db1d39 |
566 | The normal way to find your own hostname is to call the C<`hostname`> |
567 | program. While sometimes expedient, this has some problems, such as |
568 | not knowing whether you've got the canonical name or not. It's one of |
569 | those tradeoffs of convenience versus portability. |
68dc0745 |
570 | |
571 | The Sys::Hostname module (part of the standard perl distribution) will |
572 | give you the hostname after which you can find out the IP address |
573 | (assuming you have working DNS) with a gethostbyname() call. |
574 | |
575 | use Socket; |
576 | use Sys::Hostname; |
577 | my $host = hostname(); |
65acb1b1 |
578 | my $addr = inet_ntoa(scalar gethostbyname($host || 'localhost')); |
68dc0745 |
579 | |
580 | Probably the simplest way to learn your DNS domain name is to grok |
581 | it out of /etc/resolv.conf, at least under Unix. Of course, this |
582 | assumes several things about your resolv.conf configuration, including |
583 | that it exists. |
584 | |
585 | (We still need a good DNS domain name-learning method for non-Unix |
586 | systems.) |
587 | |
588 | =head2 How do I fetch a news article or the active newsgroups? |
589 | |
590 | Use the Net::NNTP or News::NNTPClient modules, both available from CPAN. |
a6dd486b |
591 | This can make tasks like fetching the newsgroup list as simple as |
68dc0745 |
592 | |
593 | perl -MNews::NNTPClient |
594 | -e 'print News::NNTPClient->new->list("newsgroups")' |
595 | |
596 | =head2 How do I fetch/put an FTP file? |
597 | |
598 | LWP::Simple (available from CPAN) can fetch but not put. Net::FTP (also |
599 | available from CPAN) is more complex but can put as well as fetch. |
600 | |
601 | =head2 How can I do RPC in Perl? |
602 | |
a6dd486b |
603 | A DCE::RPC module is being developed (but is not yet available) and |
68dc0745 |
604 | will be released as part of the DCE-Perl package (available from |
65acb1b1 |
605 | CPAN). The rpcgen suite, available from CPAN/authors/id/JAKE/, is |
606 | an RPC stub generator and includes an RPC::ONC module. |
68dc0745 |
607 | |
608 | =head1 AUTHOR AND COPYRIGHT |
609 | |
65acb1b1 |
610 | Copyright (c) 1997-1999 Tom Christiansen and Nathan Torkington. |
5a964f20 |
611 | All rights reserved. |
612 | |
5a7beb56 |
613 | This documentation is free; you can redistribute it and/or modify it |
614 | under the same terms as Perl itself. |
5a964f20 |
615 | |
616 | Irrespective of its distribution, all code examples in this file |
617 | are hereby placed into the public domain. You are permitted and |
618 | encouraged to use this code in your own programs for fun |
619 | or for profit as you see fit. A simple comment in the code giving |
620 | credit would be courteous but is not required. |