5 B<CGI::Carp> - CGI routines for writing to the HTTPD (or other) error log
11 croak "We're outta here!";
12 confess "It was my fault: $!";
13 carp "It was your fault!";
17 use CGI::Carp qw(cluck);
18 cluck "I wouldn't do that if I were you";
20 use CGI::Carp qw(fatalsToBrowser);
21 die "Fatal error messages are now sent to browser";
25 CGI scripts have a nasty habit of leaving warning messages in the error
26 logs that are neither time stamped nor fully identified. Tracking down
27 the script that caused the error is a pain. This fixes that. Replace
36 And the standard warn(), die (), croak(), confess() and carp() calls
37 will automagically be replaced with functions that write out nicely
38 time-stamped messages to the HTTP server error log.
42 [Fri Nov 17 21:40:43 1995] test.pl: I'm confused at test.pl line 3.
43 [Fri Nov 17 21:40:43 1995] test.pl: Got an error message: Permission denied.
44 [Fri Nov 17 21:40:43 1995] test.pl: I'm dying.
46 =head1 REDIRECTING ERROR MESSAGES
48 By default, error messages are sent to STDERR. Most HTTPD servers
49 direct STDERR to the server's error log. Some applications may wish
50 to keep private error logs, distinct from the server's error log, or
51 they may wish to direct error messages to STDOUT so that the browser
54 The C<carpout()> function is provided for this purpose. Since
55 carpout() is not exported by default, you must import it explicitly by
58 use CGI::Carp qw(carpout);
60 The carpout() function requires one argument, which should be a
61 reference to an open filehandle for writing errors. It should be
62 called in a C<BEGIN> block at the top of the CGI application so that
63 compiler errors will be caught. Example:
66 use CGI::Carp qw(carpout);
67 open(LOG, ">>/usr/local/cgi-logs/mycgi-log") or
68 die("Unable to open mycgi-log: $!\n");
72 carpout() does not handle file locking on the log for you at this point.
74 The real STDERR is not closed -- it is moved to CGI::Carp::SAVEERR. Some
75 servers, when dealing with CGI scripts, close their connection to the
76 browser when the script closes STDOUT and STDERR. CGI::Carp::SAVEERR is there to
77 prevent this from happening prematurely.
79 You can pass filehandles to carpout() in a variety of ways. The "correct"
80 way according to Tom Christiansen is to pass a reference to a filehandle
85 This looks weird to mere mortals however, so the following syntaxes are
92 carpout(\'main::LOG');
96 FileHandle and other objects work as well.
98 Use of carpout() is not great for performance, so it is recommended
99 for debugging purposes or for moderate-use applications. A future
100 version of this module may delay redirecting STDERR until one of the
101 CGI::Carp methods is called to prevent the performance hit.
103 =head1 MAKING PERL ERRORS APPEAR IN THE BROWSER WINDOW
105 If you want to send fatal (die, confess) errors to the browser, ask to
106 import the special "fatalsToBrowser" subroutine:
108 use CGI::Carp qw(fatalsToBrowser);
109 die "Bad error here";
111 Fatal errors will now be echoed to the browser as well as to the log. CGI::Carp
112 arranges to send a minimal HTTP header to the browser so that even errors that
113 occur in the early compile phase will be seen.
114 Nonfatal errors will still be directed to the log file only (unless redirected
117 Note that fatalsToBrowser does B<not> work with mod_perl version 2.0
120 =head2 Changing the default message
122 By default, the software error message is followed by a note to
123 contact the Webmaster by e-mail with the time and date of the error.
124 If this message is not to your liking, you can change it using the
125 set_message() routine. This is not imported by default; you should
126 import it on the use() line:
128 use CGI::Carp qw(fatalsToBrowser set_message);
129 set_message("It's not a bug, it's a feature!");
131 You may also pass in a code reference in order to create a custom
132 error message. At run time, your code will be called with the text
133 of the error message that caused the script to die. Example:
135 use CGI::Carp qw(fatalsToBrowser set_message);
139 print "<h1>Oh gosh</h1>";
140 print "<p>Got an error: $msg</p>";
142 set_message(\&handle_errors);
145 In order to correctly intercept compile-time errors, you should call
146 set_message() from within a BEGIN{} block.
148 =head1 DOING MORE THAN PRINTING A MESSAGE IN THE EVENT OF PERL ERRORS
150 If fatalsToBrowser in conjunction with set_message does not provide
151 you with all of the functionality you need, you can go one step
152 further by specifying a function to be executed any time a script
153 calls "die", has a syntax error, or dies unexpectedly at runtime
154 with a line like "undef->explode();".
156 use CGI::Carp qw(set_die_handler);
160 print "content-type: text/html\n\n";
161 print "<h1>Oh gosh</h1>";
162 print "<p>Got an error: $msg</p>";
164 #proceed to send an email to a system administrator,
165 #write a detailed message to the browser and/or a log,
168 set_die_handler(\&handle_errors);
171 Notice that if you use set_die_handler(), you must handle sending
172 HTML headers to the browser yourself if you are printing a message.
174 If you use set_die_handler(), you will most likely interfere with
175 the behavior of fatalsToBrowser, so you must use this or that, not
178 Using set_die_handler() sets SIG{__DIE__} (as does fatalsToBrowser),
179 and there is only one SIG{__DIE__}. This means that if you are
180 attempting to set SIG{__DIE__} yourself, you may interfere with
181 this module's functionality, or this module may interfere with
182 your module's functionality.
184 =head1 MAKING WARNINGS APPEAR AS HTML COMMENTS
186 It is now also possible to make non-fatal errors appear as HTML
187 comments embedded in the output of your program. To enable this
188 feature, export the new "warningsToBrowser" subroutine. Since sending
189 warnings to the browser before the HTTP headers have been sent would
190 cause an error, any warnings are stored in an internal buffer until
191 you call the warningsToBrowser() subroutine with a true argument:
193 use CGI::Carp qw(fatalsToBrowser warningsToBrowser);
194 use CGI qw(:standard);
196 warningsToBrowser(1);
198 You may also give a false argument to warningsToBrowser() to prevent
199 warnings from being sent to the browser while you are printing some
200 content where HTML comments are not allowed:
202 warningsToBrowser(0); # disable warnings
203 print "<script type=\"text/javascript\"><!--\n";
204 print_some_javascript_code();
205 print "//--></script>\n";
206 warningsToBrowser(1); # re-enable warnings
208 Note: In this respect warningsToBrowser() differs fundamentally from
209 fatalsToBrowser(), which you should never call yourself!
211 =head1 OVERRIDING THE NAME OF THE PROGRAM
213 CGI::Carp includes the name of the program that generated the error or
214 warning in the messages written to the log and the browser window.
215 Sometimes, Perl can get confused about what the actual name of the
216 executed program was. In these cases, you can override the program
217 name that CGI::Carp will use for all messages.
219 The quick way to do that is to tell CGI::Carp the name of the program
220 in its use statement. You can do that by adding
221 "name=cgi_carp_log_name" to your "use" statement. For example:
223 use CGI::Carp qw(name=cgi_carp_log_name);
225 . If you want to change the program name partway through the program,
226 you can use the C<set_progname()> function instead. It is not
227 exported by default, you must import it explicitly by saying
229 use CGI::Carp qw(set_progname);
231 Once you've done that, you can change the logged name of the program
232 at any time by calling
234 set_progname(new_program_name);
236 You can set the program back to the default by calling
240 Note that this override doesn't happen until after the program has
241 compiled, so any compile-time errors will still show up with the
242 non-overridden program name
246 1.29 Patch from Peter Whaite to fix the unfixable problem of CGI::Carp
247 not behaving correctly in an eval() context.
249 1.05 carpout() added and minor corrections by Marc Hedlund
250 <hedlund@best.com> on 11/26/95.
252 1.06 fatalsToBrowser() no longer aborts for fatal errors within
255 1.08 set_message() added and carpout() expanded to allow for FileHandle
258 1.09 set_message() now allows users to pass a code REFERENCE for
259 really custom error messages. croak and carp are now
260 exported by default. Thanks to Gunther Birznieks for the
263 1.10 Patch from Chris Dean (ctdean@cogit.com) to allow
264 module to run correctly under mod_perl.
266 1.11 Changed order of > and < escapes.
268 1.12 Changed die() on line 217 to CORE::die to avoid B<-w> warning.
270 1.13 Added cluck() to make the module orthogonal with Carp.
271 More mod_perl related fixes.
273 1.20 Patch from Ilmari Karonen (perl@itz.pp.sci.fi): Added
274 warningsToBrowser(). Replaced <CODE> tags with <PRE> in
275 fatalsToBrowser() output.
277 1.23 ineval() now checks both $^S and inspects the message for the "eval" pattern
278 (hack alert!) in order to accommodate various combinations of Perl and
281 1.24 Patch from Scott Gifford (sgifford@suspectclass.com): Add support
282 for overriding program name.
284 1.26 Replaced CORE::GLOBAL::die with the evil $SIG{__DIE__} because the
285 former isn't working in some people's hands. There is no such thing
286 as reliable exception handling in Perl.
288 1.27 Replaced tell STDOUT with bytes=tell STDOUT.
292 Copyright 1995-2002, Lincoln D. Stein. All rights reserved.
294 This library is free software; you can redistribute it and/or modify
295 it under the same terms as Perl itself.
297 Address bug reports and comments to: lstein@cshl.org
301 Carp, CGI::Base, CGI::BasePlus, CGI::Request, CGI::MiniSvr, CGI::Form,
303 if (defined($CGI::Carp::PROGNAME))
305 $file = $CGI::Carp::PROGNAME;
315 *CORE::GLOBAL::die = \&CGI::Carp::die;
321 @EXPORT = qw(confess croak carp);
322 @EXPORT_OK = qw(carpout fatalsToBrowser warningsToBrowser wrap set_message set_die_handler set_progname cluck ^name= die);
324 $main::SIG{__WARN__}=\&CGI::Carp::warn;
326 $CGI::Carp::VERSION = '1.29';
327 $CGI::Carp::CUSTOM_MSG = undef;
328 $CGI::Carp::DIE_HANDLER = undef;
331 # fancy import routine detects and handles 'errorWrap' specially.
336 if (@name=grep(/^name=/,@_))
338 my($n) = (split(/=/,$name[0]))[1];
340 @_=grep(!/^name=/,@_);
343 grep($routines{$_}++,@_,@EXPORT);
344 $WRAP++ if $routines{'fatalsToBrowser'} || $routines{'wrap'};
345 $WARN++ if $routines{'warningsToBrowser'};
346 my($oldlevel) = $Exporter::ExportLevel;
347 $Exporter::ExportLevel = 1;
348 Exporter::import($pkg,keys %routines);
349 $Exporter::ExportLevel = $oldlevel;
350 $main::SIG{__DIE__} =\&CGI::Carp::die if $routines{'fatalsToBrowser'};
351 # $pkg->export('CORE::GLOBAL','die');
354 # These are the originals
355 sub realwarn { CORE::warn(@_); }
356 sub realdie { CORE::die(@_); }
360 my($pack,$file,$line,$sub) = caller($level);
361 my($dev,$dirs,$id) = File::Spec->splitpath($file);
362 return ($file,$line,$id);
366 my $time = scalar(localtime);
368 my ($id,$pack,$file,$dev,$dirs);
369 if (defined($CGI::Carp::PROGNAME)) {
370 $id = $CGI::Carp::PROGNAME;
374 ($pack,$file) = caller($frame++);
377 ($dev,$dirs,$id) = File::Spec->splitpath($id);
378 return "[$time] $id: ";
382 $CGI::Carp::PROGNAME = shift;
383 return $CGI::Carp::PROGNAME;
389 my($file,$line,$id) = id(1);
390 $message .= " at $file line $line.\n" unless $message=~/\n$/;
391 _warn($message) if $WARN;
393 $message=~s/^/$stamp/gm;
399 if ($EMIT_WARNINGS) {
400 # We need to mangle the message a bit to make it a valid HTML
401 # comment. This is done by substituting similar-looking ISO
402 # 8859-1 characters for <, > and -. This is a hack.
403 $msg =~ tr/<>-/\253\273\255/;
405 print STDOUT "<!-- warning: $msg -->\n";
407 push @WARNINGS, $msg;
412 # The mod_perl package Apache::Registry loads CGI programs by calling
413 # eval. These evals don't count when looking at the stack backtrace.
415 my $message = Carp::longmess();
416 $message =~ s,eval[^\n]+(ModPerl|Apache)/(?:Registry|Dispatch)\w*\.pm.*,,s
417 if exists $ENV{MOD_PERL};
422 (exists $ENV{MOD_PERL} ? 0 : $^S) || _longmess() =~ /eval [\{\']/m
426 my ($arg,@rest) = @_;
429 &$DIE_HANDLER($arg,@rest);
434 $arg = join("",($arg,@rest)) || "Died";
435 my($file,$line,$id) = id(1);
436 $arg .= " at $file line $line.\n" unless $arg=~/\n$/;
445 $arg = join("", ($arg,@rest));
446 my($file,$line,$id) = id(1);
447 $arg .= " at $file line $line." unless $arg=~/\n$/;
448 &fatalsToBrowser($arg) if $WRAP;
449 if (($arg =~ /\n$/) || !exists($ENV{MOD_PERL})) {
461 $CGI::Carp::CUSTOM_MSG = shift;
462 return $CGI::Carp::CUSTOM_MSG;
465 sub set_die_handler {
467 my ($handler) = shift;
469 #setting SIG{__DIE__} here is necessary to catch runtime
470 #errors which are not called by literally saying "die",
471 #such as the line "undef->explode();". however, doing this
472 #will interfere with fatalsToBrowser, which also sets
473 #SIG{__DIE__} in the import() function above (or the
474 #import() function above may interfere with this). for
475 #this reason, you should choose to either set the die
476 #handler here, or use fatalsToBrowser, not both.
477 $main::SIG{__DIE__} = $handler;
479 $CGI::Carp::DIE_HANDLER = $handler;
481 return $CGI::Carp::DIE_HANDLER;
484 sub confess { CGI::Carp::die Carp::longmess @_; }
485 sub croak { CGI::Carp::die Carp::shortmess @_; }
486 sub carp { CGI::Carp::warn Carp::shortmess @_; }
487 sub cluck { CGI::Carp::warn Carp::longmess @_; }
489 # We have to be ready to accept a filehandle as a reference
493 my($no) = fileno(to_filehandle($in));
494 realdie("Invalid filehandle $in\n") unless defined $no;
496 open(SAVEERR, ">&STDERR");
497 open(STDERR, ">&$no") or
498 ( print SAVEERR "Unable to redirect STDERR: $!\n" and exit(1) );
501 sub warningsToBrowser {
502 $EMIT_WARNINGS = @_ ? shift : 1;
503 _warn(shift @WARNINGS) while $EMIT_WARNINGS and @WARNINGS;
507 sub fatalsToBrowser {
513 my($wm) = $ENV{SERVER_ADMIN} ?
514 qq[the webmaster (<a href="mailto:$ENV{SERVER_ADMIN}">$ENV{SERVER_ADMIN}</a>)] :
515 "this site's webmaster";
516 my ($outer_message) = <<END;
517 For help, please send mail to $wm, giving this error message
518 and the time and date of the error.
521 my $mod_perl = exists $ENV{MOD_PERL};
524 if (ref($CUSTOM_MSG) eq 'CODE') {
525 print STDOUT "Content-type: text/html\n\n"
527 &$CUSTOM_MSG($msg); # nicer to perl 5.003 users
530 $outer_message = $CUSTOM_MSG;
535 <h1>Software error:</h1>
545 if ($ENV{MOD_PERL_API_VERSION} && $ENV{MOD_PERL_API_VERSION} == 2) {
547 require Apache2::RequestRec;
548 require Apache2::RequestIO;
549 require Apache2::RequestUtil;
551 require ModPerl::Util;
552 require Apache2::Response;
553 $r = Apache2::RequestUtil->request;
556 $r = Apache->request;
558 # If bytes have already been sent, then
559 # we print the message out directly.
560 # Otherwise we make a custom error
561 # handler to produce the doc for us.
562 if ($r->bytes_sent) {
564 $mod_perl == 2 ? ModPerl::Util::exit(0) : $r->exit;
566 # MSIE won't display a custom 500 response unless it is >512 bytes!
567 if ($ENV{HTTP_USER_AGENT} =~ /MSIE/) {
568 $mess = "<!-- " . (' ' x 513) . " -->\n$mess";
570 $r->custom_response(500,$mess);
573 my $bytes_written = eval{tell STDOUT};
574 if (defined $bytes_written && $bytes_written > 0) {
578 print STDOUT "Content-type: text/html\n\n";
583 warningsToBrowser(1); # emit warnings before dying
586 # Cut and paste from CGI.pm so that we don't have the overhead of
587 # always loading the entire CGI module.
590 return undef unless $thingy;
591 return $thingy if UNIVERSAL::isa($thingy,'GLOB');
592 return $thingy if UNIVERSAL::isa($thingy,'FileHandle');
595 while (my $package = caller($caller++)) {
596 my($tmp) = $thingy=~/[\':]/ ? $thingy : "$package\:\:$thingy";
597 return $tmp if defined(fileno($tmp));