


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


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...



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               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:










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           :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



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                           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 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:



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       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)".

       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



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       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.




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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> .












































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