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| 129 | .\" ======================================================================== |
| 130 | .\" |
| 131 | .IX Title "PERLFAQ9 1" |
| 132 | .TH PERLFAQ9 1 "2002-06-08" "perl v5.8.0" "Perl Programmers Reference Guide" |
| 133 | .SH "NAME" |
| 134 | perlfaq9 \- Networking ($Revision: 1.9 $, $Date: 2002/04/07 18:46:13 $) |
| 135 | .SH "DESCRIPTION" |
| 136 | .IX Header "DESCRIPTION" |
| 137 | This section deals with questions related to networking, the internet, |
| 138 | and a few on the web. |
| 139 | .Sh "What is the correct form of response from a \s-1CGI\s0 script?" |
| 140 | .IX Subsection "What is the correct form of response from a CGI script?" |
| 141 | (Alan Flavell <flavell+www@a5.ph.gla.ac.uk> answers...) |
| 142 | .PP |
| 143 | The Common Gateway Interface (\s-1CGI\s0) specifies a software interface between |
| 144 | a program (\*(L"\s-1CGI\s0 script\*(R") and a web server (\s-1HTTPD\s0). It is not specific |
| 145 | to Perl, and has its own FAQs and tutorials, and usenet group, |
| 146 | comp.infosystems.www.authoring.cgi |
| 147 | .PP |
| 148 | The original \s-1CGI\s0 specification is at: http://hoohoo.ncsa.uiuc.edu/cgi/ |
| 149 | .PP |
| 150 | Current best-practice \s-1RFC\s0 draft at: http://CGI\-Spec.Golux.Com/ |
| 151 | .PP |
| 152 | Other relevant documentation listed in: http://www.perl.org/CGI_MetaFAQ.html |
| 153 | .PP |
| 154 | These Perl FAQs very selectively cover some \s-1CGI\s0 issues. However, Perl |
| 155 | programmers are strongly advised to use the \s-1CGI\s0.pm module, to take care |
| 156 | of the details for them. |
| 157 | .PP |
| 158 | The similarity between \s-1CGI\s0 response headers (defined in the \s-1CGI\s0 |
| 159 | specification) and \s-1HTTP\s0 response headers (defined in the \s-1HTTP\s0 |
| 160 | specification, \s-1RFC2616\s0) is intentional, but can sometimes be confusing. |
| 161 | .PP |
| 162 | The \s-1CGI\s0 specification defines two kinds of script: the \*(L"Parsed Header\*(R" |
| 163 | script, and the \*(L"Non Parsed Header\*(R" (\s-1NPH\s0) script. Check your server |
| 164 | documentation to see what it supports. \*(L"Parsed Header\*(R" scripts are |
| 165 | simpler in various respects. The \s-1CGI\s0 specification allows any of the |
| 166 | usual newline representations in the \s-1CGI\s0 response (it's the server's |
| 167 | job to create an accurate \s-1HTTP\s0 response based on it). So \*(L"\en\*(R" written in |
| 168 | text mode is technically correct, and recommended. \s-1NPH\s0 scripts are more |
| 169 | tricky: they must put out a complete and accurate set of \s-1HTTP\s0 |
| 170 | transaction response headers; the \s-1HTTP\s0 specification calls for records |
| 171 | to be terminated with carriage-return and line\-feed, i.e \s-1ASCII\s0 \e015\e012 |
| 172 | written in binary mode. |
| 173 | .PP |
| 174 | Using \s-1CGI\s0.pm gives excellent platform independence, including \s-1EBCDIC\s0 |
| 175 | systems. \s-1CGI\s0.pm selects an appropriate newline representation |
| 176 | ($CGI::CRLF) and sets binmode as appropriate. |
| 177 | .Sh "My \s-1CGI\s0 script runs from the command line but not the browser. (500 Server Error)" |
| 178 | .IX Subsection "My CGI script runs from the command line but not the browser. (500 Server Error)" |
| 179 | Several things could be wrong. You can go through the \*(L"Troubleshooting |
| 180 | Perl \s-1CGI\s0 scripts\*(R" guide at |
| 181 | .PP |
| 182 | .Vb 1 |
| 183 | \& http://www.perl.org/troubleshooting_CGI.html |
| 184 | .Ve |
| 185 | .PP |
| 186 | If, after that, you can demonstrate that you've read the FAQs and that |
| 187 | your problem isn't something simple that can be easily answered, you'll |
| 188 | probably receive a courteous and useful reply to your question if you |
| 189 | post it on comp.infosystems.www.authoring.cgi (if it's something to do |
| 190 | with \s-1HTTP\s0 or the \s-1CGI\s0 protocols). Questions that appear to be Perl |
| 191 | questions but are really \s-1CGI\s0 ones that are posted to comp.lang.perl.misc |
| 192 | are not so well received. |
| 193 | .PP |
| 194 | The useful FAQs, related documents, and troubleshooting guides are |
| 195 | listed in the \s-1CGI\s0 Meta \s-1FAQ:\s0 |
| 196 | .PP |
| 197 | .Vb 1 |
| 198 | \& http://www.perl.org/CGI_MetaFAQ.html |
| 199 | .Ve |
| 200 | .Sh "How can I get better error messages from a \s-1CGI\s0 program?" |
| 201 | .IX Subsection "How can I get better error messages from a CGI program?" |
| 202 | Use the CGI::Carp module. It replaces \f(CW\*(C`warn\*(C'\fR and \f(CW\*(C`die\*(C'\fR, plus the |
| 203 | normal Carp modules \f(CW\*(C`carp\*(C'\fR, \f(CW\*(C`croak\*(C'\fR, and \f(CW\*(C`confess\*(C'\fR functions with |
| 204 | more verbose and safer versions. It still sends them to the normal |
| 205 | server error log. |
| 206 | .PP |
| 207 | .Vb 3 |
| 208 | \& use CGI::Carp; |
| 209 | \& warn "This is a complaint"; |
| 210 | \& die "But this one is serious"; |
| 211 | .Ve |
| 212 | .PP |
| 213 | The following use of CGI::Carp also redirects errors to a file of your choice, |
| 214 | placed in a \s-1BEGIN\s0 block to catch compile-time warnings as well: |
| 215 | .PP |
| 216 | .Vb 6 |
| 217 | \& BEGIN { |
| 218 | \& use CGI::Carp qw(carpout); |
| 219 | \& open(LOG, ">>/var/local/cgi-logs/mycgi-log") |
| 220 | \& or die "Unable to append to mycgi-log: $!\en"; |
| 221 | \& carpout(*LOG); |
| 222 | \& } |
| 223 | .Ve |
| 224 | .PP |
| 225 | You can even arrange for fatal errors to go back to the client browser, |
| 226 | which is nice for your own debugging, but might confuse the end user. |
| 227 | .PP |
| 228 | .Vb 2 |
| 229 | \& use CGI::Carp qw(fatalsToBrowser); |
| 230 | \& die "Bad error here"; |
| 231 | .Ve |
| 232 | .PP |
| 233 | Even if the error happens before you get the \s-1HTTP\s0 header out, the module |
| 234 | will try to take care of this to avoid the dreaded server 500 errors. |
| 235 | Normal warnings still go out to the server error log (or wherever |
| 236 | you've sent them with \f(CW\*(C`carpout\*(C'\fR) with the application name and date |
| 237 | stamp prepended. |
| 238 | .Sh "How do I remove \s-1HTML\s0 from a string?" |
| 239 | .IX Subsection "How do I remove HTML from a string?" |
| 240 | The most correct way (albeit not the fastest) is to use HTML::Parser |
| 241 | from \s-1CPAN\s0. Another mostly correct |
| 242 | way is to use HTML::FormatText which not only removes \s-1HTML\s0 but also |
| 243 | attempts to do a little simple formatting of the resulting plain text. |
| 244 | .PP |
| 245 | Many folks attempt a simple-minded regular expression approach, like |
| 246 | \&\f(CW\*(C`s/<.*?>//g\*(C'\fR, but that fails in many cases because the tags |
| 247 | may continue over line breaks, they may contain quoted angle\-brackets, |
| 248 | or \s-1HTML\s0 comment may be present. Plus, folks forget to convert |
| 249 | entities\*(--like \f(CW\*(C`<\*(C'\fR for example. |
| 250 | .PP |
| 251 | Here's one \*(L"simple\-minded\*(R" approach, that works for most files: |
| 252 | .PP |
| 253 | .Vb 2 |
| 254 | \& #!/usr/bin/perl -p0777 |
| 255 | \& s/<(?:[^>'"]*|(['"]).*?\e1)*>//gs |
| 256 | .Ve |
| 257 | .PP |
| 258 | If you want a more complete solution, see the 3\-stage striphtml |
| 259 | program in |
| 260 | http://www.cpan.org/authors/Tom_Christiansen/scripts/striphtml.gz |
| 261 | \&. |
| 262 | .PP |
| 263 | Here are some tricky cases that you should think about when picking |
| 264 | a solution: |
| 265 | .PP |
| 266 | .Vb 1 |
| 267 | \& <IMG SRC = "foo.gif" ALT = "A > B"> |
| 268 | .Ve |
| 269 | .PP |
| 270 | .Vb 2 |
| 271 | \& <IMG SRC = "foo.gif" |
| 272 | \& ALT = "A > B"> |
| 273 | .Ve |
| 274 | .PP |
| 275 | .Vb 1 |
| 276 | \& <!-- <A comment> --> |
| 277 | .Ve |
| 278 | .PP |
| 279 | .Vb 1 |
| 280 | \& <script>if (a<b && a>c)</script> |
| 281 | .Ve |
| 282 | .PP |
| 283 | .Vb 1 |
| 284 | \& <# Just data #> |
| 285 | .Ve |
| 286 | .PP |
| 287 | .Vb 1 |
| 288 | \& <![INCLUDE CDATA [ >>>>>>>>>>>> ]]> |
| 289 | .Ve |
| 290 | .PP |
| 291 | If \s-1HTML\s0 comments include other tags, those solutions would also break |
| 292 | on text like this: |
| 293 | .PP |
| 294 | .Vb 3 |
| 295 | \& <!-- This section commented out. |
| 296 | \& <B>You can't see me!</B> |
| 297 | \& --> |
| 298 | .Ve |
| 299 | .Sh "How do I extract URLs?" |
| 300 | .IX Subsection "How do I extract URLs?" |
| 301 | You can easily extract all sorts of URLs from \s-1HTML\s0 with |
| 302 | \&\f(CW\*(C`HTML::SimpleLinkExtor\*(C'\fR which handles anchors, images, objects, |
| 303 | frames, and many other tags that can contain a \s-1URL\s0. If you need |
| 304 | anything more complex, you can create your own subclass of |
| 305 | \&\f(CW\*(C`HTML::LinkExtor\*(C'\fR or \f(CW\*(C`HTML::Parser\*(C'\fR. You might even use |
| 306 | \&\f(CW\*(C`HTML::SimpleLinkExtor\*(C'\fR as an example for something specifically |
| 307 | suited to your needs. |
| 308 | .PP |
| 309 | Less complete solutions involving regular expressions can save |
| 310 | you a lot of processing time if you know that the input is simple. One |
| 311 | solution from Tom Christiansen runs 100 times faster than most |
| 312 | module based approaches but only extracts URLs from anchors where the first |
| 313 | attribute is \s-1HREF\s0 and there are no other attributes. |
| 314 | .PP |
| 315 | .Vb 7 |
| 316 | \& #!/usr/bin/perl -n00 |
| 317 | \& # qxurl - tchrist@perl.com |
| 318 | \& print "$2\en" while m{ |
| 319 | \& < \es* |
| 320 | \& A \es+ HREF \es* = \es* (["']) (.*?) \e1 |
| 321 | \& \es* > |
| 322 | \& }gsix; |
| 323 | .Ve |
| 324 | .Sh "How do I download a file from the user's machine? How do I open a file on another machine?" |
| 325 | .IX Subsection "How do I download a file from the user's machine? How do I open a file on another machine?" |
| 326 | In the context of an \s-1HTML\s0 form, you can use what's known as |
| 327 | \&\fBmultipart/form\-data\fR encoding. The \s-1CGI\s0.pm module (available from |
| 328 | \&\s-1CPAN\s0) supports this in the \fIstart_multipart_form()\fR method, which isn't |
| 329 | the same as the \fIstartform()\fR method. |
| 330 | .Sh "How do I make a pop-up menu in \s-1HTML\s0?" |
| 331 | .IX Subsection "How do I make a pop-up menu in HTML?" |
| 332 | Use the \fB<\s-1SELECT\s0>\fR and \fB<\s-1OPTION\s0>\fR tags. The \s-1CGI\s0.pm |
| 333 | module (available from \s-1CPAN\s0) supports this widget, as well as many |
| 334 | others, including some that it cleverly synthesizes on its own. |
| 335 | .Sh "How do I fetch an \s-1HTML\s0 file?" |
| 336 | .IX Subsection "How do I fetch an HTML file?" |
| 337 | One approach, if you have the lynx text-based \s-1HTML\s0 browser installed |
| 338 | on your system, is this: |
| 339 | .PP |
| 340 | .Vb 2 |
| 341 | \& $html_code = `lynx -source $url`; |
| 342 | \& $text_data = `lynx -dump $url`; |
| 343 | .Ve |
| 344 | .PP |
| 345 | The libwww-perl (\s-1LWP\s0) modules from \s-1CPAN\s0 provide a more powerful way |
| 346 | to do this. They don't require lynx, but like lynx, can still work |
| 347 | through proxies: |
| 348 | .PP |
| 349 | .Vb 3 |
| 350 | \& # simplest version |
| 351 | \& use LWP::Simple; |
| 352 | \& $content = get($URL); |
| 353 | .Ve |
| 354 | .PP |
| 355 | .Vb 3 |
| 356 | \& # or print HTML from a URL |
| 357 | \& use LWP::Simple; |
| 358 | \& getprint "http://www.linpro.no/lwp/"; |
| 359 | .Ve |
| 360 | .PP |
| 361 | .Vb 11 |
| 362 | \& # or print ASCII from HTML from a URL |
| 363 | \& # also need HTML-Tree package from CPAN |
| 364 | \& use LWP::Simple; |
| 365 | \& use HTML::Parser; |
| 366 | \& use HTML::FormatText; |
| 367 | \& my ($html, $ascii); |
| 368 | \& $html = get("http://www.perl.com/"); |
| 369 | \& defined $html |
| 370 | \& or die "Can't fetch HTML from http://www.perl.com/"; |
| 371 | \& $ascii = HTML::FormatText->new->format(parse_html($html)); |
| 372 | \& print $ascii; |
| 373 | .Ve |
| 374 | .Sh "How do I automate an \s-1HTML\s0 form submission?" |
| 375 | .IX Subsection "How do I automate an HTML form submission?" |
| 376 | If you're submitting values using the \s-1GET\s0 method, create a \s-1URL\s0 and encode |
| 377 | the form using the \f(CW\*(C`query_form\*(C'\fR method: |
| 378 | .PP |
| 379 | .Vb 2 |
| 380 | \& use LWP::Simple; |
| 381 | \& use URI::URL; |
| 382 | .Ve |
| 383 | .PP |
| 384 | .Vb 3 |
| 385 | \& my $url = url('http://www.perl.com/cgi-bin/cpan_mod'); |
| 386 | \& $url->query_form(module => 'DB_File', readme => 1); |
| 387 | \& $content = get($url); |
| 388 | .Ve |
| 389 | .PP |
| 390 | If you're using the \s-1POST\s0 method, create your own user agent and encode |
| 391 | the content appropriately. |
| 392 | .PP |
| 393 | .Vb 2 |
| 394 | \& use HTTP::Request::Common qw(POST); |
| 395 | \& use LWP::UserAgent; |
| 396 | .Ve |
| 397 | .PP |
| 398 | .Vb 4 |
| 399 | \& $ua = LWP::UserAgent->new(); |
| 400 | \& my $req = POST 'http://www.perl.com/cgi-bin/cpan_mod', |
| 401 | \& [ module => 'DB_File', readme => 1 ]; |
| 402 | \& $content = $ua->request($req)->as_string; |
| 403 | .Ve |
| 404 | .Sh "How do I decode or create those %\-encodings on the web?" |
| 405 | .IX Subsection "How do I decode or create those %-encodings on the web?" |
| 406 | If you are writing a \s-1CGI\s0 script, you should be using the \s-1CGI\s0.pm module |
| 407 | that comes with perl, or some other equivalent module. The \s-1CGI\s0 module |
| 408 | automatically decodes queries for you, and provides an \fIescape()\fR |
| 409 | function to handle encoding. |
| 410 | .PP |
| 411 | The best source of detailed information on \s-1URI\s0 encoding is \s-1RFC\s0 2396. |
| 412 | Basically, the following substitutions do it: |
| 413 | .PP |
| 414 | .Vb 1 |
| 415 | \& s/([^\ew()'*~!.-])/sprintf '%%%02x', ord $1/eg; # encode |
| 416 | .Ve |
| 417 | .PP |
| 418 | .Vb 1 |
| 419 | \& s/%([A-Fa-f\ed]{2})/chr hex $1/eg; # decode |
| 420 | .Ve |
| 421 | .PP |
| 422 | However, you should only apply them to individual \s-1URI\s0 components, not |
| 423 | the entire \s-1URI\s0, otherwise you'll lose information and generally mess |
| 424 | things up. If that didn't explain it, don't worry. Just go read |
| 425 | section 2 of the \s-1RFC\s0, it's probably the best explanation there is. |
| 426 | .PP |
| 427 | \&\s-1RFC\s0 2396 also contains a lot of other useful information, including a |
| 428 | regexp for breaking any arbitrary \s-1URI\s0 into components (Appendix B). |
| 429 | .Sh "How do I redirect to another page?" |
| 430 | .IX Subsection "How do I redirect to another page?" |
| 431 | Specify the complete \s-1URL\s0 of the destination (even if it is on the same |
| 432 | server). This is one of the two different kinds of \s-1CGI\s0 \*(L"Location:\*(R" |
| 433 | responses which are defined in the \s-1CGI\s0 specification for a Parsed Headers |
| 434 | script. The other kind (an absolute URLpath) is resolved internally to |
| 435 | the server without any \s-1HTTP\s0 redirection. The \s-1CGI\s0 specifications do not |
| 436 | allow relative URLs in either case. |
| 437 | .PP |
| 438 | Use of \s-1CGI\s0.pm is strongly recommended. This example shows redirection |
| 439 | with a complete \s-1URL\s0. This redirection is handled by the web browser. |
| 440 | .PP |
| 441 | .Vb 1 |
| 442 | \& use CGI qw/:standard/; |
| 443 | .Ve |
| 444 | .PP |
| 445 | .Vb 2 |
| 446 | \& my $url = 'http://www.cpan.org/'; |
| 447 | \& print redirect($url); |
| 448 | .Ve |
| 449 | .PP |
| 450 | This example shows a redirection with an absolute URLpath. This |
| 451 | redirection is handled by the local web server. |
| 452 | .PP |
| 453 | .Vb 2 |
| 454 | \& my $url = '/CPAN/index.html'; |
| 455 | \& print redirect($url); |
| 456 | .Ve |
| 457 | .PP |
| 458 | But if coded directly, it could be as follows (the final \*(L"\en\*(R" is |
| 459 | shown separately, for clarity), using either a complete \s-1URL\s0 or |
| 460 | an absolute URLpath. |
| 461 | .PP |
| 462 | .Vb 2 |
| 463 | \& print "Location: $url\en"; # CGI response header |
| 464 | \& print "\en"; # end of headers |
| 465 | .Ve |
| 466 | .Sh "How do I put a password on my web pages?" |
| 467 | .IX Subsection "How do I put a password on my web pages?" |
| 468 | That depends. You'll need to read the documentation for your web |
| 469 | server, or perhaps check some of the other FAQs referenced above. |
| 470 | .Sh "How do I edit my .htpasswd and .htgroup files with Perl?" |
| 471 | .IX Subsection "How do I edit my .htpasswd and .htgroup files with Perl?" |
| 472 | The HTTPD::UserAdmin and HTTPD::GroupAdmin modules provide a |
| 473 | consistent \s-1OO\s0 interface to these files, regardless of how they're |
| 474 | stored. Databases may be text, dbm, Berkeley \s-1DB\s0 or any database with |
| 475 | a \s-1DBI\s0 compatible driver. HTTPD::UserAdmin supports files used by the |
| 476 | `Basic' and `Digest' authentication schemes. Here's an example: |
| 477 | .PP |
| 478 | .Vb 4 |
| 479 | \& use HTTPD::UserAdmin (); |
| 480 | \& HTTPD::UserAdmin |
| 481 | \& ->new(DB => "/foo/.htpasswd") |
| 482 | \& ->add($username => $password); |
| 483 | .Ve |
| 484 | .Sh "How do I make sure users can't enter values into a form that cause my \s-1CGI\s0 script to do bad things?" |
| 485 | .IX Subsection "How do I make sure users can't enter values into a form that cause my CGI script to do bad things?" |
| 486 | See the security references listed in the \s-1CGI\s0 Meta \s-1FAQ\s0 |
| 487 | .PP |
| 488 | .Vb 1 |
| 489 | \& http://www.perl.org/CGI_MetaFAQ.html |
| 490 | .Ve |
| 491 | .Sh "How do I parse a mail header?" |
| 492 | .IX Subsection "How do I parse a mail header?" |
| 493 | For a quick-and-dirty solution, try this solution derived |
| 494 | from \*(L"split\*(R" in perlfunc: |
| 495 | .PP |
| 496 | .Vb 4 |
| 497 | \& $/ = ''; |
| 498 | \& $header = <MSG>; |
| 499 | \& $header =~ s/\en\es+/ /g; # merge continuation lines |
| 500 | \& %head = ( UNIX_FROM_LINE, split /^([-\ew]+):\es*/m, $header ); |
| 501 | .Ve |
| 502 | .PP |
| 503 | That solution doesn't do well if, for example, you're trying to |
| 504 | maintain all the Received lines. A more complete approach is to use |
| 505 | the Mail::Header module from \s-1CPAN\s0 (part of the MailTools package). |
| 506 | .Sh "How do I decode a \s-1CGI\s0 form?" |
| 507 | .IX Subsection "How do I decode a CGI form?" |
| 508 | You use a standard module, probably \s-1CGI\s0.pm. Under no circumstances |
| 509 | should you attempt to do so by hand! |
| 510 | .PP |
| 511 | You'll see a lot of \s-1CGI\s0 programs that blindly read from \s-1STDIN\s0 the number |
| 512 | of bytes equal to \s-1CONTENT_LENGTH\s0 for POSTs, or grab \s-1QUERY_STRING\s0 for |
| 513 | decoding GETs. These programs are very poorly written. They only work |
| 514 | sometimes. They typically forget to check the return value of the \fIread()\fR |
| 515 | system call, which is a cardinal sin. They don't handle \s-1HEAD\s0 requests. |
| 516 | They don't handle multipart forms used for file uploads. They don't deal |
| 517 | with \s-1GET/POST\s0 combinations where query fields are in more than one place. |
| 518 | They don't deal with keywords in the query string. |
| 519 | .PP |
| 520 | In short, they're bad hacks. Resist them at all costs. Please do not be |
| 521 | tempted to reinvent the wheel. Instead, use the \s-1CGI\s0.pm or CGI_Lite.pm |
| 522 | (available from \s-1CPAN\s0), or if you're trapped in the module-free land |
| 523 | of perl1 .. perl4, you might look into cgi\-lib.pl (available from |
| 524 | http://cgi\-lib.stanford.edu/cgi\-lib/ ). |
| 525 | .PP |
| 526 | Make sure you know whether to use a \s-1GET\s0 or a \s-1POST\s0 in your form. |
| 527 | GETs should only be used for something that doesn't update the server. |
| 528 | Otherwise you can get mangled databases and repeated feedback mail |
| 529 | messages. The fancy word for this is ``idempotency''. This simply |
| 530 | means that there should be no difference between making a \s-1GET\s0 request |
| 531 | for a particular \s-1URL\s0 once or multiple times. This is because the |
| 532 | \&\s-1HTTP\s0 protocol definition says that a \s-1GET\s0 request may be cached by the |
| 533 | browser, or server, or an intervening proxy. \s-1POST\s0 requests cannot be |
| 534 | cached, because each request is independent and matters. Typically, |
| 535 | \&\s-1POST\s0 requests change or depend on state on the server (query or update |
| 536 | a database, send mail, or purchase a computer). |
| 537 | .Sh "How do I check a valid mail address?" |
| 538 | .IX Subsection "How do I check a valid mail address?" |
| 539 | You can't, at least, not in real time. Bummer, eh? |
| 540 | .PP |
| 541 | Without sending mail to the address and seeing whether there's a human |
| 542 | on the other hand to answer you, you cannot determine whether a mail |
| 543 | address is valid. Even if you apply the mail header standard, you |
| 544 | can have problems, because there are deliverable addresses that aren't |
| 545 | \&\s-1RFC\-822\s0 (the mail header standard) compliant, and addresses that aren't |
| 546 | deliverable which are compliant. |
| 547 | .PP |
| 548 | Many are tempted to try to eliminate many frequently-invalid |
| 549 | mail addresses with a simple regex, such as |
| 550 | \&\f(CW\*(C`/^[\ew.\-]+\e@(?:[\ew\-]+\e.)+\ew+$/\*(C'\fR. It's a very bad idea. However, |
| 551 | this also throws out many valid ones, and says nothing about |
| 552 | potential deliverability, so it is not suggested. Instead, see |
| 553 | http://www.cpan.org/authors/Tom_Christiansen/scripts/ckaddr.gz , |
| 554 | which actually checks against the full \s-1RFC\s0 spec (except for nested |
| 555 | comments), looks for addresses you may not wish to accept mail to |
| 556 | (say, Bill Clinton or your postmaster), and then makes sure that the |
| 557 | hostname given can be looked up in the \s-1DNS\s0 \s-1MX\s0 records. It's not fast, |
| 558 | but it works for what it tries to do. |
| 559 | .PP |
| 560 | Our best advice for verifying a person's mail address is to have them |
| 561 | enter their address twice, just as you normally do to change a password. |
| 562 | This usually weeds out typos. If both versions match, send |
| 563 | mail to that address with a personal message that looks somewhat like: |
| 564 | .PP |
| 565 | .Vb 1 |
| 566 | \& Dear someuser@host.com, |
| 567 | .Ve |
| 568 | .PP |
| 569 | .Vb 5 |
| 570 | \& Please confirm the mail address you gave us Wed May 6 09:38:41 |
| 571 | \& MDT 1998 by replying to this message. Include the string |
| 572 | \& "Rumpelstiltskin" in that reply, but spelled in reverse; that is, |
| 573 | \& start with "Nik...". Once this is done, your confirmed address will |
| 574 | \& be entered into our records. |
| 575 | .Ve |
| 576 | .PP |
| 577 | If you get the message back and they've followed your directions, |
| 578 | you can be reasonably assured that it's real. |
| 579 | .PP |
| 580 | A related strategy that's less open to forgery is to give them a \s-1PIN\s0 |
| 581 | (personal \s-1ID\s0 number). Record the address and \s-1PIN\s0 (best that it be a |
| 582 | random one) for later processing. In the mail you send, ask them to |
| 583 | include the \s-1PIN\s0 in their reply. But if it bounces, or the message is |
| 584 | included via a ``vacation'' script, it'll be there anyway. So it's |
| 585 | best to ask them to mail back a slight alteration of the \s-1PIN\s0, such as |
| 586 | with the characters reversed, one added or subtracted to each digit, etc. |
| 587 | .Sh "How do I decode a \s-1MIME/BASE64\s0 string?" |
| 588 | .IX Subsection "How do I decode a MIME/BASE64 string?" |
| 589 | The MIME\-Base64 package (available from \s-1CPAN\s0) handles this as well as |
| 590 | the \s-1MIME/QP\s0 encoding. Decoding \s-1BASE64\s0 becomes as simple as: |
| 591 | .PP |
| 592 | .Vb 2 |
| 593 | \& use MIME::Base64; |
| 594 | \& $decoded = decode_base64($encoded); |
| 595 | .Ve |
| 596 | .PP |
| 597 | The MIME-Tools package (available from \s-1CPAN\s0) supports extraction with |
| 598 | decoding of \s-1BASE64\s0 encoded attachments and content directly from email |
| 599 | messages. |
| 600 | .PP |
| 601 | If the string to decode is short (less than 84 bytes long) |
| 602 | a more direct approach is to use the \fIunpack()\fR function's \*(L"u\*(R" |
| 603 | format after minor transliterations: |
| 604 | .PP |
| 605 | .Vb 4 |
| 606 | \& tr#A-Za-z0-9+/##cd; # remove non-base64 chars |
| 607 | \& tr#A-Za-z0-9+/# -_#; # convert to uuencoded format |
| 608 | \& $len = pack("c", 32 + 0.75*length); # compute length byte |
| 609 | \& print unpack("u", $len . $_); # uudecode and print |
| 610 | .Ve |
| 611 | .Sh "How do I return the user's mail address?" |
| 612 | .IX Subsection "How do I return the user's mail address?" |
| 613 | On systems that support getpwuid, the $< variable, and the |
| 614 | Sys::Hostname module (which is part of the standard perl distribution), |
| 615 | you can probably try using something like this: |
| 616 | .PP |
| 617 | .Vb 2 |
| 618 | \& use Sys::Hostname; |
| 619 | \& $address = sprintf('%s@%s', scalar getpwuid($<), hostname); |
| 620 | .Ve |
| 621 | .PP |
| 622 | Company policies on mail address can mean that this generates addresses |
| 623 | that the company's mail system will not accept, so you should ask for |
| 624 | users' mail addresses when this matters. Furthermore, not all systems |
| 625 | on which Perl runs are so forthcoming with this information as is Unix. |
| 626 | .PP |
| 627 | The Mail::Util module from \s-1CPAN\s0 (part of the MailTools package) provides a |
| 628 | \&\fImailaddress()\fR function that tries to guess the mail address of the user. |
| 629 | It makes a more intelligent guess than the code above, using information |
| 630 | given when the module was installed, but it could still be incorrect. |
| 631 | Again, the best way is often just to ask the user. |
| 632 | .Sh "How do I send mail?" |
| 633 | .IX Subsection "How do I send mail?" |
| 634 | Use the \f(CW\*(C`sendmail\*(C'\fR program directly: |
| 635 | .PP |
| 636 | .Vb 6 |
| 637 | \& open(SENDMAIL, "|/usr/lib/sendmail -oi -t -odq") |
| 638 | \& or die "Can't fork for sendmail: $!\en"; |
| 639 | \& print SENDMAIL <<"EOF"; |
| 640 | \& From: User Originating Mail <me\e@host> |
| 641 | \& To: Final Destination <you\e@otherhost> |
| 642 | \& Subject: A relevant subject line |
| 643 | .Ve |
| 644 | .PP |
| 645 | .Vb 4 |
| 646 | \& Body of the message goes here after the blank line |
| 647 | \& in as many lines as you like. |
| 648 | \& EOF |
| 649 | \& close(SENDMAIL) or warn "sendmail didn't close nicely"; |
| 650 | .Ve |
| 651 | .PP |
| 652 | The \fB\-oi\fR option prevents sendmail from interpreting a line consisting |
| 653 | of a single dot as \*(L"end of message\*(R". The \fB\-t\fR option says to use the |
| 654 | headers to decide who to send the message to, and \fB\-odq\fR says to put |
| 655 | the message into the queue. This last option means your message won't |
| 656 | be immediately delivered, so leave it out if you want immediate |
| 657 | delivery. |
| 658 | .PP |
| 659 | Alternate, less convenient approaches include calling mail (sometimes |
| 660 | called mailx) directly or simply opening up port 25 have having an |
| 661 | intimate conversation between just you and the remote \s-1SMTP\s0 daemon, |
| 662 | probably sendmail. |
| 663 | .PP |
| 664 | Or you might be able use the \s-1CPAN\s0 module Mail::Mailer: |
| 665 | .PP |
| 666 | .Vb 1 |
| 667 | \& use Mail::Mailer; |
| 668 | .Ve |
| 669 | .PP |
| 670 | .Vb 8 |
| 671 | \& $mailer = Mail::Mailer->new(); |
| 672 | \& $mailer->open({ From => $from_address, |
| 673 | \& To => $to_address, |
| 674 | \& Subject => $subject, |
| 675 | \& }) |
| 676 | \& or die "Can't open: $!\en"; |
| 677 | \& print $mailer $body; |
| 678 | \& $mailer->close(); |
| 679 | .Ve |
| 680 | .PP |
| 681 | The Mail::Internet module uses Net::SMTP which is less Unix-centric than |
| 682 | Mail::Mailer, but less reliable. Avoid raw \s-1SMTP\s0 commands. There |
| 683 | are many reasons to use a mail transport agent like sendmail. These |
| 684 | include queuing, \s-1MX\s0 records, and security. |
| 685 | .Sh "How do I use \s-1MIME\s0 to make an attachment to a mail message?" |
| 686 | .IX Subsection "How do I use MIME to make an attachment to a mail message?" |
| 687 | This answer is extracted directly from the MIME::Lite documentation. |
| 688 | Create a multipart message (i.e., one with attachments). |
| 689 | .PP |
| 690 | .Vb 1 |
| 691 | \& use MIME::Lite; |
| 692 | .Ve |
| 693 | .PP |
| 694 | .Vb 8 |
| 695 | \& ### Create a new multipart message: |
| 696 | \& $msg = MIME::Lite->new( |
| 697 | \& From =>'me@myhost.com', |
| 698 | \& To =>'you@yourhost.com', |
| 699 | \& Cc =>'some@other.com, some@more.com', |
| 700 | \& Subject =>'A message with 2 parts...', |
| 701 | \& Type =>'multipart/mixed' |
| 702 | \& ); |
| 703 | .Ve |
| 704 | .PP |
| 705 | .Vb 8 |
| 706 | \& ### Add parts (each "attach" has same arguments as "new"): |
| 707 | \& $msg->attach(Type =>'TEXT', |
| 708 | \& Data =>"Here's the GIF file you wanted" |
| 709 | \& ); |
| 710 | \& $msg->attach(Type =>'image/gif', |
| 711 | \& Path =>'aaa000123.gif', |
| 712 | \& Filename =>'logo.gif' |
| 713 | \& ); |
| 714 | .Ve |
| 715 | .PP |
| 716 | .Vb 1 |
| 717 | \& $text = $msg->as_string; |
| 718 | .Ve |
| 719 | .PP |
| 720 | MIME::Lite also includes a method for sending these things. |
| 721 | .PP |
| 722 | .Vb 1 |
| 723 | \& $msg->send; |
| 724 | .Ve |
| 725 | .PP |
| 726 | This defaults to using \fIsendmail\fR\|(1) but can be customized to use |
| 727 | \&\s-1SMTP\s0 via Net::SMTP. |
| 728 | .Sh "How do I read mail?" |
| 729 | .IX Subsection "How do I read mail?" |
| 730 | While you could use the Mail::Folder module from \s-1CPAN\s0 (part of the |
| 731 | MailFolder package) or the Mail::Internet module from \s-1CPAN\s0 (also part |
| 732 | of the MailTools package), often a module is overkill. Here's a |
| 733 | mail sorter. |
| 734 | .PP |
| 735 | .Vb 15 |
| 736 | \& #!/usr/bin/perl |
| 737 | \& # bysub1 - simple sort by subject |
| 738 | \& my(@msgs, @sub); |
| 739 | \& my $msgno = -1; |
| 740 | \& $/ = ''; # paragraph reads |
| 741 | \& while (<>) { |
| 742 | \& if (/^From/m) { |
| 743 | \& /^Subject:\es*(?:Re:\es*)*(.*)/mi; |
| 744 | \& $sub[++$msgno] = lc($1) || ''; |
| 745 | \& } |
| 746 | \& $msgs[$msgno] .= $_; |
| 747 | \& } |
| 748 | \& for my $i (sort { $sub[$a] cmp $sub[$b] || $a <=> $b } (0 .. $#msgs)) { |
| 749 | \& print $msgs[$i]; |
| 750 | \& } |
| 751 | .Ve |
| 752 | .PP |
| 753 | Or more succinctly, |
| 754 | .PP |
| 755 | .Vb 6 |
| 756 | \& #!/usr/bin/perl -n00 |
| 757 | \& # bysub2 - awkish sort-by-subject |
| 758 | \& BEGIN { $msgno = -1 } |
| 759 | \& $sub[++$msgno] = (/^Subject:\es*(?:Re:\es*)*(.*)/mi)[0] if /^From/m; |
| 760 | \& $msg[$msgno] .= $_; |
| 761 | \& END { print @msg[ sort { $sub[$a] cmp $sub[$b] || $a <=> $b } (0 .. $#msg) ] } |
| 762 | .Ve |
| 763 | .Sh "How do I find out my hostname/domainname/IP address?" |
| 764 | .IX Subsection "How do I find out my hostname/domainname/IP address?" |
| 765 | The normal way to find your own hostname is to call the \f(CW`hostname`\fR |
| 766 | program. While sometimes expedient, this has some problems, such as |
| 767 | not knowing whether you've got the canonical name or not. It's one of |
| 768 | those tradeoffs of convenience versus portability. |
| 769 | .PP |
| 770 | The Sys::Hostname module (part of the standard perl distribution) will |
| 771 | give you the hostname after which you can find out the \s-1IP\s0 address |
| 772 | (assuming you have working \s-1DNS\s0) with a \fIgethostbyname()\fR call. |
| 773 | .PP |
| 774 | .Vb 4 |
| 775 | \& use Socket; |
| 776 | \& use Sys::Hostname; |
| 777 | \& my $host = hostname(); |
| 778 | \& my $addr = inet_ntoa(scalar gethostbyname($host || 'localhost')); |
| 779 | .Ve |
| 780 | .PP |
| 781 | Probably the simplest way to learn your \s-1DNS\s0 domain name is to grok |
| 782 | it out of /etc/resolv.conf, at least under Unix. Of course, this |
| 783 | assumes several things about your resolv.conf configuration, including |
| 784 | that it exists. |
| 785 | .PP |
| 786 | (We still need a good \s-1DNS\s0 domain name-learning method for non-Unix |
| 787 | systems.) |
| 788 | .Sh "How do I fetch a news article or the active newsgroups?" |
| 789 | .IX Subsection "How do I fetch a news article or the active newsgroups?" |
| 790 | Use the Net::NNTP or News::NNTPClient modules, both available from \s-1CPAN\s0. |
| 791 | This can make tasks like fetching the newsgroup list as simple as |
| 792 | .PP |
| 793 | .Vb 2 |
| 794 | \& perl -MNews::NNTPClient |
| 795 | \& -e 'print News::NNTPClient->new->list("newsgroups")' |
| 796 | .Ve |
| 797 | .Sh "How do I fetch/put an \s-1FTP\s0 file?" |
| 798 | .IX Subsection "How do I fetch/put an FTP file?" |
| 799 | LWP::Simple (available from \s-1CPAN\s0) can fetch but not put. Net::FTP (also |
| 800 | available from \s-1CPAN\s0) is more complex but can put as well as fetch. |
| 801 | .Sh "How can I do \s-1RPC\s0 in Perl?" |
| 802 | .IX Subsection "How can I do RPC in Perl?" |
| 803 | A \s-1DCE::RPC\s0 module is being developed (but is not yet available) and |
| 804 | will be released as part of the DCE-Perl package (available from |
| 805 | \&\s-1CPAN\s0). The rpcgen suite, available from CPAN/authors/id/JAKE/, is |
| 806 | an \s-1RPC\s0 stub generator and includes an \s-1RPC::ONC\s0 module. |
| 807 | .SH "AUTHOR AND COPYRIGHT" |
| 808 | .IX Header "AUTHOR AND COPYRIGHT" |
| 809 | Copyright (c) 1997\-2002 Tom Christiansen and Nathan Torkington. |
| 810 | All rights reserved. |
| 811 | .PP |
| 812 | This documentation is free; you can redistribute it and/or modify it |
| 813 | under the same terms as Perl itself. |
| 814 | .PP |
| 815 | Irrespective of its distribution, all code examples in this file |
| 816 | are hereby placed into the public domain. You are permitted and |
| 817 | encouraged to use this code in your own programs for fun |
| 818 | or for profit as you see fit. A simple comment in the code giving |
| 819 | credit would be courteous but is not required. |