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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 builtin
       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)