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autodie::exception(3pm)Perl Programmers Reference Guideautodie::exception(3pm)

NAME
       autodie::exception - Exceptions from autodying functions.

SYNOPSIS
	   eval {
	       use autodie;

	       open(my $fh, '<', 'some_file.txt');

	       ...
	   };

	   if (my $E = $@) {
	       say "Ooops!  ",$E->caller," had problems: $@";
	   }

DESCRIPTION
       When an autodie enabled function fails, it generates an
       "autodie::exception" object.  This can be interrogated to determine
       further information about the error that occurred.

       This document is broken into two sections; those methods that are most
       useful to the end-developer, and those methods for anyone wishing to
       subclass or get very familiar with "autodie::exception".

   Common Methods
       These methods are intended to be used in the everyday dealing of
       exceptions.

       The following assume that the error has been copied into a separate
       scalar:

	   if ($E = $@) {
	       ...
	   }

       This is not required, but is recommended in case any code is called
       which may reset or alter $@.

       args

	   my $array_ref = $E->args;

       Provides a reference to the arguments passed to the subroutine that
       died.

       function

	   my $sub = $E->function;

       The subroutine (including package) that threw the exception.

       file

	   my $file = $E->file;

       The file in which the error occurred (eg, "myscript.pl" or
       "MyTest.pm").

       package

	   my $package = $E->package;

       The package from which the exceptional subroutine was called.

       caller

	   my $caller = $E->caller;

       The subroutine that called the exceptional code.

       line

	   my $line = $E->line;

       The line in "$E->file" where the exceptional code was called.

       context

	   my $context = $E->context;

       The context in which the subroutine was called.	This can be 'list',
       'scalar', or undefined (unknown).  It will never be 'void', as
       "autodie" always captures the return value in one way or another.

       return

	   my $return_value = $E->return;

       The value(s) returned by the failed subroutine.	When the subroutine
       was called in a list context, this will always be a reference to an
       array containing the results.  When the subroutine was called in a
       scalar context, this will be the actual scalar returned.

       errno

	   my $errno = $E->errno;

       The value of $! at the time when the exception occurred.

       NOTE: This method will leave the main "autodie::exception" class and
       become part of a role in the future.  You should only call "errno" for
       exceptions where $! would reasonably have been set on failure.

       eval_error

	   my $old_eval_error = $E->eval_error;

       The contents of $@ immediately after autodie triggered an exception.
       This may be useful when dealing with modules such as Text::Balanced
       that set (but do not throw) $@ on error.

       matches

	   if ( $e->matches('open') ) { ... }

	   if ( $e ~~ 'open' ) { ... }

       "matches" is used to determine whether a given exception matches a
       particular role.	 On Perl 5.10, using smart-match ("~~") with an
       "autodie::exception" object will use "matches" underneath.

       An exception is considered to match a string if:

       ·   For a string not starting with a colon, the string exactly matches
	   the package and subroutine that threw the exception.	 For example,
	   "MyModule::log".  If the string does not contain a package name,
	   "CORE::" is assumed.

       ·   For a string that does start with a colon, if the subroutine
	   throwing the exception does that behaviour.	For example, the
	   "CORE::open" subroutine does ":file", ":io" and ":all".

	   See "CATEGORIES" in autodie for futher information.

   Advanced methods
       The following methods, while usable from anywhere, are primarily
       intended for developers wishing to subclass "autodie::exception", write
       code that registers custom error messages, or otherwise work closely
       with the "autodie::exception" model.

       register

	   autodie::exception->register( 'CORE::open' => \&mysub );

       The "register" method allows for the registration of a message handler
       for a given subroutine.	The full subroutine name including the package
       should be used.

       Registered message handlers will receive the "autodie::exception"
       object as the first parameter.

       add_file_and_line

	   say "Problem occurred",$@->add_file_and_line;

       Returns the string " at %s line %d", where %s is replaced with the
       filename, and %d is replaced with the line number.

       Primarily intended for use by format handlers.

       stringify

	   say "The error was: ",$@->stringify;

       Formats the error as a human readable string.  Usually there's no
       reason to call this directly, as it is used automatically if an
       "autodie::exception" object is ever used as a string.

       Child classes can override this method to change how they're
       stringified.

       format_default

	   my $error_string = $E->format_default;

       This produces the default error string for the given exception, without
       using any registered message handlers.  It is primarily intended to be
       called from a message handler when they have been passed an exception
       they don't want to format.

       Child classes can override this method to change how default messages
       are formatted.

       new

	   my $error = autodie::exception->new(
	       args => \@_,
	       function => "CORE::open",
	       errno => $!,
	       context => 'scalar',
	       return => undef,
	   );

       Creates a new "autodie::exception" object.  Normally called directly
       from an autodying function.  The "function" argument is required, its
       the function we were trying to call that generated the exception.  The
       "args" parameter is optional.

       The "errno" value is optional.  In versions of "autodie::exception"
       1.99 and earlier the code would try to automatically use the current
       value of $!, but this was unreliable and is no longer supported.

       Atrributes such as package, file, and caller are determined
       automatically, and cannot be specified.

SEE ALSO
       autodie, autodie::exception::system

LICENSE
       Copyright (C)2008 Paul Fenwick

       This is free software.  You may modify and/or redistribute this code
       under the same terms as Perl 5.10 itself, or, at your option, any later
       version of Perl 5.

AUTHOR
       Paul Fenwick <pjf@perltraining.com.au>

perl v5.16.2			  2012-10-25	       autodie::exception(3pm)
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