autodie man page on MacOSX

Man page or keyword search:  
man Server   23457 pages
apropos Keyword Search (all sections)
Output format
MacOSX logo
[printable version]

autodie(3pm)	       Perl Programmers Reference Guide		  autodie(3pm)

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
			   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:

       ·   The command does not start.

       ·   The command is killed by a signal.

       ·   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)".

       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
       <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 v5.16.2			  2012-10-25			  autodie(3pm)
[top]

List of man pages available for MacOSX

Copyright (c) for man pages and the logo by the respective OS vendor.

For those who want to learn more, the polarhome community provides shell access and support.

[legal] [privacy] [GNU] [policy] [cookies] [netiquette] [sponsors] [FAQ]
Tweet
Polarhome, production since 1999.
Member of Polarhome portal.
Based on Fawad Halim's script.
...................................................................
Vote for polarhome
Free Shell Accounts :: the biggest list on the net