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autodie(3)		       User Contributed Perl Documentation		       autodie(3)

NAME
       autodie - Replace functions with ones that succeed or die with lexical scope

SYNOPSIS
	   use autodie; 	   # Recommended: implies 'use autodie qw(:default)'

	   use autodie qw(:all);   # Recommended more: defaults and system/exec.

	   use autodie qw(open close);	 # open/close succeed or die

	   open(my $fh, "<", $filename); # No need to check!

	   {
	       no autodie qw(open);	     # open failures won't die
	       open(my $fh, "<", $filename); # Could fail silently!
	       no autodie;		     # disable all autodies
	   }

DESCRIPTION
	       bIlujDI' yIchegh()Qo'; yIHegh()!

	       It is better to die() than to return() in failure.

		       -- Klingon programming proverb.

       The "autodie" pragma provides a convenient way to replace functions that normally return
       false on failure with equivalents that throw an exception on failure.

       The "autodie" pragma has lexical scope, meaning that functions and subroutines altered
       with "autodie" will only change their behaviour until the end of the enclosing block,
       file, or "eval".

       If "system" is specified as an argument to "autodie", then it uses IPC::System::Simple to
       do the heavy lifting.  See the description of that module for more information.

EXCEPTIONS
       Exceptions produced by the "autodie" pragma are members of the autodie::exception class.
       The preferred way to work with these exceptions under Perl 5.10 is as follows:

	   use feature qw(switch);

	   eval {
	       use autodie;

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

	       my @records = <$fh>;

	       # Do things with @records...

	       close($fh);

	   };

	   given ($@) {
	       when (undef)   { say "No error"; 		   }
	       when ('open')  { say "Error from open";		   }
	       when (':io')   { say "Non-open, IO error.";	   }
	       when (':all')  { say "All other autodie errors."    }
	       default	      { say "Not an autodie error at all." }
	   }

       Under Perl 5.8, the "given/when" structure is not available, so the following structure
       may be used:

	   eval {
	       use autodie;

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

	       my @records = <$fh>;

	       # Do things with @records...

	       close($fh);
	   };

	   if ($@ and $@->isa('autodie::exception')) {
	       if ($@->matches('open')) { print "Error from open\n";   }
	       if ($@->matches(':io' )) { print "Non-open, IO error."; }
	   } elsif ($@) {
	       # A non-autodie exception.
	   }

       See autodie::exception for further information on interrogating exceptions.

CATEGORIES
       Autodie uses a simple set of categories to group together similar built-ins.  Requesting a
       category type (starting with a colon) will enable autodie for all built-ins beneath that
       category.  For example, requesting ":file" will enable autodie for "close", "fcntl",
       "fileno", "open" and "sysopen".

       The categories are currently:

	   :all
	       :default
		   :io
		       read
		       seek
		       sysread
		       sysseek
		       syswrite
		       :dbm
			   dbmclose
			   dbmopen
		       :file
			   binmode
			   close
			   chmod
			   chown
			   fcntl
			   fileno
			   flock
			   ioctl
			   open
			   sysopen
			   truncate
		       :filesys
			   chdir
			   closedir
			   opendir
			   link
			   mkdir
			   readlink
			   rename
			   rmdir
			   symlink
			   unlink
		       :ipc
			   pipe
			   :msg
			       msgctl
			       msgget
			       msgrcv
			       msgsnd
			   :semaphore
			       semctl
			       semget
			       semop
			   :shm
			       shmctl
			       shmget
			       shmread
		       :socket
			   accept
			   bind
			   connect
			   getsockopt
			   listen
			   recv
			   send
			   setsockopt
			   shutdown
			   socketpair
		   :threads
		       fork
	       :system
		   system
		   exec

       Note that while the above category system is presently a strict hierarchy, this should not
       be assumed.

       A plain "use autodie" implies "use autodie qw(:default)".  Note that "system" and "exec"
       are not enabled by default.  "system" requires the optional IPC::System::Simple module to
       be installed, and enabling "system" or "exec" will invalidate their exotic forms.  See
       "BUGS" below for more details.

       The syntax:

	   use autodie qw(:1.994);

       allows the ":default" list from a particular version to be used.  This provides the
       convenience of using the default methods, but the surety that no behavorial changes will
       occur if the "autodie" module is upgraded.

       "autodie" can be enabled for all of Perl's built-ins, including "system" and "exec" with:

	   use autodie qw(:all);

FUNCTION SPECIFIC NOTES
   flock
       It is not considered an error for "flock" to return false if it fails due to an
       "EWOULDBLOCK" (or equivalent) condition.  This means one can still use the common
       convention of testing the return value of "flock" when called with the "LOCK_NB" option:

	   use autodie;

	   if ( flock($fh, LOCK_EX | LOCK_NB) ) {
	       # We have a lock
	   }

       Autodying "flock" will generate an exception if "flock" returns false with any other
       error.

   system/exec
       The "system" built-in is considered to have failed in the following circumstances:

       o   The command does not start.

       o   The command is killed by a signal.

       o   The command returns a non-zero exit value (but see below).

       On success, the autodying form of "system" returns the exit value rather than the contents
       of $?.

       Additional allowable exit values can be supplied as an optional first argument to
       autodying "system":

	   system( [ 0, 1, 2 ], $cmd, @args);  # 0,1,2 are good exit values

       "autodie" uses the IPC::System::Simple module to change "system".  See its documentation
       for further information.

       Applying "autodie" to "system" or "exec" causes the exotic forms "system { $cmd } @args "
       or "exec { $cmd } @args" to be considered a syntax error until the end of the lexical
       scope.  If you really need to use the exotic form, you can call "CORE::system" or
       "CORE::exec" instead, or use "no autodie qw(system exec)" before calling the exotic form.

GOTCHAS
       Functions called in list context are assumed to have failed if they return an empty list,
       or a list consisting only of a single undef element.

DIAGNOSTICS
       :void cannot be used with lexical scope
	   The ":void" option is supported in Fatal, but not "autodie".  To workaround this,
	   "autodie" may be explicitly disabled until the end of the current block with "no
	   autodie".  To disable autodie for only a single function (eg, open) use "no autodie
	   qw(open)".

	   "autodie" performs no checking of called context to determine whether to throw an
	   exception; the explicitness of error handling with "autodie" is a deliberate feature.

       No user hints defined for %s
	   You've insisted on hints for user-subroutines, either by pre-pending a "!" to the
	   subroutine name itself, or earlier in the list of arguments to "autodie".  However the
	   subroutine in question does not have any hints available.

       See also "DIAGNOSTICS" in Fatal.

BUGS
       "Used only once" warnings can be generated when "autodie" or "Fatal" is used with package
       filehandles (eg, "FILE").  Scalar filehandles are strongly recommended instead.

       When using "autodie" or "Fatal" with user subroutines, the declaration of those
       subroutines must appear before the first use of "Fatal" or "autodie", or have been
       exported from a module.	Attempting to use "Fatal" or "autodie" on other user subroutines
       will result in a compile-time error.

       Due to a bug in Perl, "autodie" may "lose" any format which has the same name as an
       autodying built-in or function.

       "autodie" may not work correctly if used inside a file with a name that looks like a
       string eval, such as eval (3).

   autodie and string eval
       Due to the current implementation of "autodie", unexpected results may be seen when used
       near or with the string version of eval.  None of these bugs exist when using block eval.

       Under Perl 5.8 only, "autodie" does not propagate into string "eval" statements, although
       it can be explicitly enabled inside a string "eval".

       Under Perl 5.10 only, using a string eval when "autodie" is in effect can cause the
       autodie behaviour to leak into the surrounding scope.  This can be worked around by using
       a "no autodie" at the end of the scope to explicitly remove autodie's effects, or by
       avoiding the use of string eval.

       None of these bugs exist when using block eval.	The use of "autodie" with block eval is
       considered good practice.

   REPORTING BUGS
       Please report bugs via the CPAN Request Tracker at
       <http://rt.cpan.org/NoAuth/Bugs.html?Dist=autodie>.

FEEDBACK
       If you find this module useful, please consider rating it on the CPAN Ratings service at
       <http://cpanratings.perl.org/rate?distribution=autodie> .

       The module author loves to hear how "autodie" has made your life better (or worse).
       Feedback can be sent to <pjf@perltraining.com.au>.

AUTHOR
       Copyright 2008-2009, Paul Fenwick <pjf@perltraining.com.au>

LICENSE
       This module is free software.  You may distribute it under the same terms as Perl itself.

SEE ALSO
       Fatal, autodie::exception, autodie::hints, IPC::System::Simple

       Perl tips, autodie at <http://perltraining.com.au/tips/2008-08-20.html>

ACKNOWLEDGEMENTS
       Mark Reed and Roland Giersig -- Klingon translators.

       See the AUTHORS file for full credits.  The latest version of this file can be found at
       <http://github.com/pfenwick/autodie/tree/master/AUTHORS> .

perl v5.16.3				    2013-02-22				       autodie(3)
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