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Author image Paul Jamieson Fenwick

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(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
                :file
                    close
                    fcntl
                    fileno
                    open
                    sysopen
                :filesys
                    opendir
                :socket
                    accept
                    bind
                    connect
                    getsockopt
                    listen
                    recv
                    send
                    setsockopt
                    shutdown
                    socketpair
            :threads
                fork
        :system
            system
            exec

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.

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

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. However you can explicitly disable autodie end the end of the current block with no autodie. To disable autodie for only a single function (eg, open) use or no autodie qw(open).

See also "DIAGNOSTICS" in Fatal.

BUGS

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.

"Used only once" warnings can be generated when autodie or Fatal is used with package filehandles (eg, FILE). It's strongly recommended you use scalar filehandles 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 ue Fatal or autodie on other user subroutines will result in a compile-time error.

A TODO list of items remaining for improvement can be found in the development tree for the module at http://github.com/pfenwick/autodie/tree/master/TODO.

REPORTING BUGS

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

AUTHOR

Copyright 2008, 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, IPC::System::Simple

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/AUTHORS .