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| 103 | .ds : \\k:\h'-(\\n(.wu*8/10-\*(#H+.1m+\*(#F)'\v'-\*(#V'\z.\h'.2m+\*(#F'.\h'|\\n:u'\v'\*(#V' |
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| 128 | .rm #[ #] #H #V #F C |
| 129 | .\" ======================================================================== |
| 130 | .\" |
| 131 | .IX Title "CGI::Carp 3" |
| 132 | .TH CGI::Carp 3 "2001-09-21" "perl v5.8.8" "Perl Programmers Reference Guide" |
| 133 | .SH "NAME" |
| 134 | \&\fBCGI::Carp\fR \- CGI routines for writing to the HTTPD (or other) error log |
| 135 | .SH "SYNOPSIS" |
| 136 | .IX Header "SYNOPSIS" |
| 137 | .Vb 1 |
| 138 | \& use CGI::Carp; |
| 139 | .Ve |
| 140 | .PP |
| 141 | .Vb 5 |
| 142 | \& croak "We're outta here!"; |
| 143 | \& confess "It was my fault: $!"; |
| 144 | \& carp "It was your fault!"; |
| 145 | \& warn "I'm confused"; |
| 146 | \& die "I'm dying.\en"; |
| 147 | .Ve |
| 148 | .PP |
| 149 | .Vb 2 |
| 150 | \& use CGI::Carp qw(cluck); |
| 151 | \& cluck "I wouldn't do that if I were you"; |
| 152 | .Ve |
| 153 | .PP |
| 154 | .Vb 2 |
| 155 | \& use CGI::Carp qw(fatalsToBrowser); |
| 156 | \& die "Fatal error messages are now sent to browser"; |
| 157 | .Ve |
| 158 | .SH "DESCRIPTION" |
| 159 | .IX Header "DESCRIPTION" |
| 160 | \&\s-1CGI\s0 scripts have a nasty habit of leaving warning messages in the error |
| 161 | logs that are neither time stamped nor fully identified. Tracking down |
| 162 | the script that caused the error is a pain. This fixes that. Replace |
| 163 | the usual |
| 164 | .PP |
| 165 | .Vb 1 |
| 166 | \& use Carp; |
| 167 | .Ve |
| 168 | .PP |
| 169 | with |
| 170 | .PP |
| 171 | .Vb 1 |
| 172 | \& use CGI::Carp |
| 173 | .Ve |
| 174 | .PP |
| 175 | And the standard \fIwarn()\fR, die (), \fIcroak()\fR, \fIconfess()\fR and \fIcarp()\fR calls |
| 176 | will automagically be replaced with functions that write out nicely |
| 177 | time-stamped messages to the \s-1HTTP\s0 server error log. |
| 178 | .PP |
| 179 | For example: |
| 180 | .PP |
| 181 | .Vb 3 |
| 182 | \& [Fri Nov 17 21:40:43 1995] test.pl: I'm confused at test.pl line 3. |
| 183 | \& [Fri Nov 17 21:40:43 1995] test.pl: Got an error message: Permission denied. |
| 184 | \& [Fri Nov 17 21:40:43 1995] test.pl: I'm dying. |
| 185 | .Ve |
| 186 | .SH "REDIRECTING ERROR MESSAGES" |
| 187 | .IX Header "REDIRECTING ERROR MESSAGES" |
| 188 | By default, error messages are sent to \s-1STDERR\s0. Most \s-1HTTPD\s0 servers |
| 189 | direct \s-1STDERR\s0 to the server's error log. Some applications may wish |
| 190 | to keep private error logs, distinct from the server's error log, or |
| 191 | they may wish to direct error messages to \s-1STDOUT\s0 so that the browser |
| 192 | will receive them. |
| 193 | .PP |
| 194 | The \f(CW\*(C`carpout()\*(C'\fR function is provided for this purpose. Since |
| 195 | \&\fIcarpout()\fR is not exported by default, you must import it explicitly by |
| 196 | saying |
| 197 | .PP |
| 198 | .Vb 1 |
| 199 | \& use CGI::Carp qw(carpout); |
| 200 | .Ve |
| 201 | .PP |
| 202 | The \fIcarpout()\fR function requires one argument, which should be a |
| 203 | reference to an open filehandle for writing errors. It should be |
| 204 | called in a \f(CW\*(C`BEGIN\*(C'\fR block at the top of the \s-1CGI\s0 application so that |
| 205 | compiler errors will be caught. Example: |
| 206 | .PP |
| 207 | .Vb 6 |
| 208 | \& BEGIN { |
| 209 | \& use CGI::Carp qw(carpout); |
| 210 | \& open(LOG, ">>/usr/local/cgi-logs/mycgi-log") or |
| 211 | \& die("Unable to open mycgi-log: $!\en"); |
| 212 | \& carpout(LOG); |
| 213 | \& } |
| 214 | .Ve |
| 215 | .PP |
| 216 | \&\fIcarpout()\fR does not handle file locking on the log for you at this point. |
| 217 | .PP |
| 218 | The real \s-1STDERR\s0 is not closed \*(-- it is moved to CGI::Carp::SAVEERR. Some |
| 219 | servers, when dealing with \s-1CGI\s0 scripts, close their connection to the |
| 220 | browser when the script closes \s-1STDOUT\s0 and \s-1STDERR\s0. CGI::Carp::SAVEERR is there to |
| 221 | prevent this from happening prematurely. |
| 222 | .PP |
| 223 | You can pass filehandles to \fIcarpout()\fR in a variety of ways. The \*(L"correct\*(R" |
| 224 | way according to Tom Christiansen is to pass a reference to a filehandle |
| 225 | \&\s-1GLOB:\s0 |
| 226 | .PP |
| 227 | .Vb 1 |
| 228 | \& carpout(\e*LOG); |
| 229 | .Ve |
| 230 | .PP |
| 231 | This looks weird to mere mortals however, so the following syntaxes are |
| 232 | accepted as well: |
| 233 | .PP |
| 234 | .Vb 5 |
| 235 | \& carpout(LOG); |
| 236 | \& carpout(main::LOG); |
| 237 | \& carpout(main'LOG); |
| 238 | \& carpout(\eLOG); |
| 239 | \& carpout(\e'main::LOG'); |
| 240 | .Ve |
| 241 | .PP |
| 242 | .Vb 1 |
| 243 | \& ... and so on |
| 244 | .Ve |
| 245 | .PP |
| 246 | FileHandle and other objects work as well. |
| 247 | .PP |
| 248 | Use of \fIcarpout()\fR is not great for performance, so it is recommended |
| 249 | for debugging purposes or for moderate-use applications. A future |
| 250 | version of this module may delay redirecting \s-1STDERR\s0 until one of the |
| 251 | CGI::Carp methods is called to prevent the performance hit. |
| 252 | .SH "MAKING PERL ERRORS APPEAR IN THE BROWSER WINDOW" |
| 253 | .IX Header "MAKING PERL ERRORS APPEAR IN THE BROWSER WINDOW" |
| 254 | If you want to send fatal (die, confess) errors to the browser, ask to |
| 255 | import the special \*(L"fatalsToBrowser\*(R" subroutine: |
| 256 | .PP |
| 257 | .Vb 2 |
| 258 | \& use CGI::Carp qw(fatalsToBrowser); |
| 259 | \& die "Bad error here"; |
| 260 | .Ve |
| 261 | .PP |
| 262 | Fatal errors will now be echoed to the browser as well as to the log. CGI::Carp |
| 263 | arranges to send a minimal \s-1HTTP\s0 header to the browser so that even errors that |
| 264 | occur in the early compile phase will be seen. |
| 265 | Nonfatal errors will still be directed to the log file only (unless redirected |
| 266 | with carpout). |
| 267 | .Sh "Changing the default message" |
| 268 | .IX Subsection "Changing the default message" |
| 269 | By default, the software error message is followed by a note to |
| 270 | contact the Webmaster by e\-mail with the time and date of the error. |
| 271 | If this message is not to your liking, you can change it using the |
| 272 | \&\fIset_message()\fR routine. This is not imported by default; you should |
| 273 | import it on the \fIuse()\fR line: |
| 274 | .PP |
| 275 | .Vb 2 |
| 276 | \& use CGI::Carp qw(fatalsToBrowser set_message); |
| 277 | \& set_message("It's not a bug, it's a feature!"); |
| 278 | .Ve |
| 279 | .PP |
| 280 | You may also pass in a code reference in order to create a custom |
| 281 | error message. At run time, your code will be called with the text |
| 282 | of the error message that caused the script to die. Example: |
| 283 | .PP |
| 284 | .Vb 9 |
| 285 | \& use CGI::Carp qw(fatalsToBrowser set_message); |
| 286 | \& BEGIN { |
| 287 | \& sub handle_errors { |
| 288 | \& my $msg = shift; |
| 289 | \& print "<h1>Oh gosh</h1>"; |
| 290 | \& print "<p>Got an error: $msg</p>"; |
| 291 | \& } |
| 292 | \& set_message(\e&handle_errors); |
| 293 | \& } |
| 294 | .Ve |
| 295 | .PP |
| 296 | In order to correctly intercept compile-time errors, you should call |
| 297 | \&\fIset_message()\fR from within a BEGIN{} block. |
| 298 | .SH "MAKING WARNINGS APPEAR AS HTML COMMENTS" |
| 299 | .IX Header "MAKING WARNINGS APPEAR AS HTML COMMENTS" |
| 300 | It is now also possible to make non-fatal errors appear as \s-1HTML\s0 |
| 301 | comments embedded in the output of your program. To enable this |
| 302 | feature, export the new \*(L"warningsToBrowser\*(R" subroutine. Since sending |
| 303 | warnings to the browser before the \s-1HTTP\s0 headers have been sent would |
| 304 | cause an error, any warnings are stored in an internal buffer until |
| 305 | you call the \fIwarningsToBrowser()\fR subroutine with a true argument: |
| 306 | .PP |
| 307 | .Vb 4 |
| 308 | \& use CGI::Carp qw(fatalsToBrowser warningsToBrowser); |
| 309 | \& use CGI qw(:standard); |
| 310 | \& print header(); |
| 311 | \& warningsToBrowser(1); |
| 312 | .Ve |
| 313 | .PP |
| 314 | You may also give a false argument to \fIwarningsToBrowser()\fR to prevent |
| 315 | warnings from being sent to the browser while you are printing some |
| 316 | content where \s-1HTML\s0 comments are not allowed: |
| 317 | .PP |
| 318 | .Vb 5 |
| 319 | \& warningsToBrowser(0); # disable warnings |
| 320 | \& print "<script type=\e"text/javascript\e"><!--\en"; |
| 321 | \& print_some_javascript_code(); |
| 322 | \& print "//--></script>\en"; |
| 323 | \& warningsToBrowser(1); # re-enable warnings |
| 324 | .Ve |
| 325 | .PP |
| 326 | Note: In this respect \fIwarningsToBrowser()\fR differs fundamentally from |
| 327 | \&\fIfatalsToBrowser()\fR, which you should never call yourself! |
| 328 | .SH "OVERRIDING THE NAME OF THE PROGRAM" |
| 329 | .IX Header "OVERRIDING THE NAME OF THE PROGRAM" |
| 330 | CGI::Carp includes the name of the program that generated the error or |
| 331 | warning in the messages written to the log and the browser window. |
| 332 | Sometimes, Perl can get confused about what the actual name of the |
| 333 | executed program was. In these cases, you can override the program |
| 334 | name that CGI::Carp will use for all messages. |
| 335 | .PP |
| 336 | The quick way to do that is to tell CGI::Carp the name of the program |
| 337 | in its use statement. You can do that by adding |
| 338 | \&\*(L"name=cgi_carp_log_name\*(R" to your \*(L"use\*(R" statement. For example: |
| 339 | .PP |
| 340 | .Vb 1 |
| 341 | \& use CGI::Carp qw(name=cgi_carp_log_name); |
| 342 | .Ve |
| 343 | .PP |
| 344 | \&. If you want to change the program name partway through the program, |
| 345 | you can use the \f(CW\*(C`set_progname()\*(C'\fR function instead. It is not |
| 346 | exported by default, you must import it explicitly by saying |
| 347 | .PP |
| 348 | .Vb 1 |
| 349 | \& use CGI::Carp qw(set_progname); |
| 350 | .Ve |
| 351 | .PP |
| 352 | Once you've done that, you can change the logged name of the program |
| 353 | at any time by calling |
| 354 | .PP |
| 355 | .Vb 1 |
| 356 | \& set_progname(new_program_name); |
| 357 | .Ve |
| 358 | .PP |
| 359 | You can set the program back to the default by calling |
| 360 | .PP |
| 361 | .Vb 1 |
| 362 | \& set_progname(undef); |
| 363 | .Ve |
| 364 | .PP |
| 365 | Note that this override doesn't happen until after the program has |
| 366 | compiled, so any compile-time errors will still show up with the |
| 367 | non-overridden program name |
| 368 | .SH "CHANGE LOG" |
| 369 | .IX Header "CHANGE LOG" |
| 370 | 1.05 \fIcarpout()\fR added and minor corrections by Marc Hedlund |
| 371 | <hedlund@best.com> on 11/26/95. |
| 372 | .PP |
| 373 | 1.06 \fIfatalsToBrowser()\fR no longer aborts for fatal errors within |
| 374 | \fIeval()\fR statements. |
| 375 | .PP |
| 376 | 1.08 \fIset_message()\fR added and \fIcarpout()\fR expanded to allow for FileHandle |
| 377 | objects. |
| 378 | .PP |
| 379 | 1.09 \fIset_message()\fR now allows users to pass a code \s-1REFERENCE\s0 for |
| 380 | really custom error messages. croak and carp are now |
| 381 | exported by default. Thanks to Gunther Birznieks for the |
| 382 | patches. |
| 383 | .PP |
| 384 | 1.10 Patch from Chris Dean (ctdean@cogit.com) to allow |
| 385 | module to run correctly under mod_perl. |
| 386 | .PP |
| 387 | 1.11 Changed order of > and < escapes. |
| 388 | .PP |
| 389 | 1.12 Changed \fIdie()\fR on line 217 to CORE::die to avoid \fB\-w\fR warning. |
| 390 | .PP |
| 391 | 1.13 Added \fIcluck()\fR to make the module orthogonal with Carp. |
| 392 | More mod_perl related fixes. |
| 393 | .PP |
| 394 | 1.20 Patch from Ilmari Karonen (perl@itz.pp.sci.fi): Added |
| 395 | \fIwarningsToBrowser()\fR. Replaced <\s-1CODE\s0> tags with <\s-1PRE\s0> in |
| 396 | \fIfatalsToBrowser()\fR output. |
| 397 | .PP |
| 398 | 1.23 \fIineval()\fR now checks both $^S and inspects the message for the \*(L"eval\*(R" pattern |
| 399 | (hack alert!) in order to accomodate various combinations of Perl and |
| 400 | mod_perl. |
| 401 | .PP |
| 402 | 1.24 Patch from Scott Gifford (sgifford@suspectclass.com): Add support |
| 403 | for overriding program name. |
| 404 | .PP |
| 405 | 1.26 Replaced CORE::GLOBAL::die with the evil \f(CW$SIG\fR{_\|_DIE_\|_} because the |
| 406 | former isn't working in some people's hands. There is no such thing |
| 407 | as reliable exception handling in Perl. |
| 408 | .PP |
| 409 | 1.27 Replaced tell \s-1STDOUT\s0 with bytes=tell \s-1STDOUT\s0. |
| 410 | .SH "AUTHORS" |
| 411 | .IX Header "AUTHORS" |
| 412 | Copyright 1995\-2002, Lincoln D. Stein. All rights reserved. |
| 413 | .PP |
| 414 | This library is free software; you can redistribute it and/or modify |
| 415 | it under the same terms as Perl itself. |
| 416 | .PP |
| 417 | Address bug reports and comments to: lstein@cshl.org |
| 418 | .SH "SEE ALSO" |
| 419 | .IX Header "SEE ALSO" |
| 420 | Carp, CGI::Base, CGI::BasePlus, CGI::Request, CGI::MiniSvr, CGI::Form, |
| 421 | CGI::Response |
| 422 | if (defined($CGI::Carp::PROGNAME)) |
| 423 | { |
| 424 | \f(CW$file\fR = \f(CW$CGI::Carp::PROGNAME\fR; |
| 425 | } |