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CGI::Carp(3)	 Perl Programmers Reference Guide    CGI::Carp(3)

NAME
       CGI::Carp - CGI routines for writing to the HTTPD (or
       other) error log

SYNOPSIS
	   use CGI::Carp;

	   croak "We're outta here!";
	   confess "It was my fault: $!";
	   carp "It was your fault!";
	   warn "I'm confused";
	   die	"I'm dying.\n";

	   use CGI::Carp qw(cluck);
	   cluck "I wouldn't do that if I were you";

	   use CGI::Carp qw(fatalsToBrowser);
	   die "Fatal error messages are now sent to browser";

DESCRIPTION
       CGI scripts have a nasty habit of leaving warning messages
       in the error logs that are neither time stamped nor fully
       identified.  Tracking down the script that caused the
       error is a pain.	 This fixes that.  Replace the usual

	   use Carp;

       with

	   use CGI::Carp

       And the standard warn(), die (), croak(), confess() and
       carp() calls will automagically be replaced with functions
       that write out nicely time-stamped messages to the HTTP
       server error log.

       For example:

	  [Fri Nov 17 21:40:43 1995] test.pl: I'm confused at test.pl line 3.
	  [Fri Nov 17 21:40:43 1995] test.pl: Got an error message: Permission denied.
	  [Fri Nov 17 21:40:43 1995] test.pl: I'm dying.

REDIRECTING ERROR MESSAGES
       By default, error messages are sent to STDERR.  Most HTTPD
       servers direct STDERR to the server's error log.	 Some
       applications may wish to keep private error logs, distinct
       from the server's error log, or they may wish to direct
       error messages to STDOUT so that the browser will receive
       them.

       The carpout() function is provided for this purpose.
       Since carpout() is not exported by default, you must

16/Sep/1999	       perl 5.005, patch 03			1

CGI::Carp(3)	 Perl Programmers Reference Guide    CGI::Carp(3)

       import it explicitly by saying

	  use CGI::Carp qw(carpout);

       The carpout() function requires one argument, which should
       be a reference to an open filehandle for writing errors.
       It should be called in a BEGIN block at the top of the CGI
       application so that compiler errors will be caught.
       Example:

	  BEGIN {
	    use CGI::Carp qw(carpout);
	    open(LOG, ">>/usr/local/cgi-logs/mycgi-log") or
	      die("Unable to open mycgi-log: $!\n");
	    carpout(LOG);
	  }

       carpout() does not handle file locking on the log for you
       at this point.

       The real STDERR is not closed -- it is moved to SAVEERR.
       Some servers, when dealing with CGI scripts, close their
       connection to the browser when the script closes STDOUT
       and STDERR.  SAVEERR is used to prevent this from
       happening prematurely.

       You can pass filehandles to carpout() in a variety of
       ways.  The "correct" way according to Tom Christiansen is
       to pass a reference to a filehandle GLOB:

	   carpout(\*LOG);

       This looks weird to mere mortals however, so the following
       syntaxes are accepted as well:

	   carpout(LOG);
	   carpout(main::LOG);
	   carpout(main'LOG);
	   carpout(\LOG);
	   carpout(\'main::LOG');

	   ... and so on

       FileHandle and other objects work as well.

       Use of carpout() is not great for performance, so it is
       recommended for debugging purposes or for moderate-use
       applications.  A future version of this module may delay
       redirecting STDERR until one of the CGI::Carp methods is
       called to prevent the performance hit.

MAKING PERL ERRORS APPEAR IN THE BROWSER WINDOW
       If you want to send fatal (die, confess) errors to the
       browser, ask to import the special "fatalsToBrowser"

16/Sep/1999	       perl 5.005, patch 03			2

CGI::Carp(3)	 Perl Programmers Reference Guide    CGI::Carp(3)

       subroutine:

	   use CGI::Carp qw(fatalsToBrowser);
	   die "Bad error here";

       Fatal errors will now be echoed to the browser as well as
       to the log.  CGI::Carp arranges to send a minimal HTTP
       header to the browser so that even errors that occur in
       the early compile phase will be seen.  Nonfatal errors
       will still be directed to the log file only (unless
       redirected with carpout).

       Changing the default message

       By default, the software error message is followed by a
       note to contact the Webmaster by e-mail with the time and
       date of the error.  If this message is not to your liking,
       you can change it using the set_message() routine.  This
       is not imported by default; you should import it on the
       use() line:

	   use CGI::Carp qw(fatalsToBrowser set_message);
	   set_message("It's not a bug, it's a feature!");

       You may also pass in a code reference in order to create a
       custom error message.  At run time, your code will be
       called with the text of the error message that caused the
       script to die.  Example:

	   use CGI::Carp qw(fatalsToBrowser set_message);
	   BEGIN {
	      sub handle_errors {
		 my $msg = shift;
		 print "<h1>Oh gosh</h1>";
		 print "Got an error: $msg";
	     }
	     set_message(\&handle_errors);
	   }

       In order to correctly intercept compile-time errors, you
       should call set_message() from within a BEGIN{} block.

CHANGE LOG
       1.05 carpout() added and minor corrections by Marc Hedlund
	    <hedlund@best.com> on 11/26/95.

       1.06 fatalsToBrowser() no longer aborts for fatal errors
       within
	    eval() statements.

       1.08 set_message() added and carpout() expanded to allow
       for FileHandle
	    objects.

16/Sep/1999	       perl 5.005, patch 03			3

CGI::Carp(3)	 Perl Programmers Reference Guide    CGI::Carp(3)

       1.09 set_message() now allows users to pass a code
       REFERENCE for
	    really custom error messages.  croak and carp are now
	    exported by default.  Thanks to Gunther Birznieks for
       the
	    patches.

       1.10 Patch from Chris Dean (ctdean@cogit.com) to allow
	    module to run correctly under mod_perl.

       1.11 Changed order of > and < escapes.

       1.12 Changed die() on line 217 to CORE::die to avoid -w
       warning.

       1.13 Added cluck() to make the module orthogonal with
       Carp.
	   More mod_perl related fixes.

AUTHORS
       Copyright 1995-1998, Lincoln D. Stein.  All rights
       reserved.

       This library is free software; you can redistribute it
       and/or modify it under the same terms as Perl itself.

       Address bug reports and comments to: lstein@cshl.org

SEE ALSO
       Carp, CGI::Base, CGI::BasePlus, CGI::Request,
       CGI::MiniSvr, CGI::Form, CGI::Response

16/Sep/1999	       perl 5.005, patch 03			4

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