package autodie;
use 5.008;
use strict;
use warnings;
use Fatal ();
our @ISA = qw(Fatal);
our $VERSION;
BEGIN {
$VERSION = '2.13';
}
use constant ERROR_WRONG_FATAL => q{
Incorrect version of Fatal.pm loaded by autodie.
The autodie pragma uses an updated version of Fatal to do its
heavy lifting. We seem to have loaded Fatal version %s, which is
probably the version that came with your version of Perl. However
autodie needs version %s, which would have come bundled with
autodie.
You may be able to solve this problem by adding the following
line of code to your main program, before any use of Fatal or
autodie.
use lib "%s";
};
# We have to check we've got the right version of Fatal before we
# try to compile the rest of our code, lest we use a constant
# that doesn't exist.
BEGIN {
# If we have the wrong Fatal, then we've probably loaded the system
# one, not our own. Complain, and give a useful hint. ;)
if ($Fatal::VERSION ne $VERSION) {
my $autodie_path = $INC{'autodie.pm'};
$autodie_path =~ s/autodie\.pm//;
require Carp;
Carp::croak sprintf(
ERROR_WRONG_FATAL, $Fatal::VERSION, $VERSION, $autodie_path
);
}
}
# When passing args to Fatal we want to keep the first arg
# (our package) in place. Hence the splice.
sub import {
splice(@_,1,0,Fatal::LEXICAL_TAG);
goto &Fatal::import;
}
sub unimport {
splice(@_,1,0,Fatal::LEXICAL_TAG);
goto &Fatal::unimport;
}
1;
__END__
=head1 NAME
autodie - Replace functions with ones that succeed or die with lexical scope
=head1 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
}
=head1 DESCRIPTION
bIlujDI' yIchegh()Qo'; yIHegh()!
It is better to die() than to return() in failure.
-- Klingon programming proverb.
The C<autodie> pragma provides a convenient way to replace functions
that normally return false on failure with equivalents that throw
an exception on failure.
The C<autodie> pragma has I<lexical scope>, meaning that functions
and subroutines altered with C<autodie> will only change their behaviour
until the end of the enclosing block, file, or C<eval>.
If C<system> is specified as an argument to C<autodie>, then it
uses L<IPC::System::Simple> to do the heavy lifting. See the
description of that module for more information.
=head1 EXCEPTIONS
Exceptions produced by the C<autodie> pragma are members of the
L<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 C<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 L<autodie::exception> for further information on interrogating
exceptions.
=head1 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 C<:file> will enable autodie for C<close>, C<fcntl>,
C<fileno>, C<open> and C<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 C<use autodie> implies C<use autodie qw(:default)>. Note that
C<system> and C<exec> are not enabled by default. C<system> requires
the optional L<IPC::System::Simple> module to be installed, and enabling
C<system> or C<exec> will invalidate their exotic forms. See L</BUGS>
below for more details.
The syntax:
use autodie qw(:1.994);
allows the C<: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 C<autodie> module is
upgraded.
C<autodie> can be enabled for all of Perl's built-ins, including
C<system> and C<exec> with:
use autodie qw(:all);
=head1 FUNCTION SPECIFIC NOTES
=head2 flock
It is not considered an error for C<flock> to return false if it fails
due to an C<EWOULDBLOCK> (or equivalent) condition. This means one can
still use the common convention of testing the return value of
C<flock> when called with the C<LOCK_NB> option:
use autodie;
if ( flock($fh, LOCK_EX | LOCK_NB) ) {
# We have a lock
}
Autodying C<flock> will generate an exception if C<flock> returns
false with any other error.
=head2 system/exec
The C<system> built-in is considered to have failed in the following
circumstances:
=over 4
=item *
The command does not start.
=item *
The command is killed by a signal.
=item *
The command returns a non-zero exit value (but see below).
=back
On success, the autodying form of C<system> returns the I<exit value>
rather than the contents of C<$?>.
Additional allowable exit values can be supplied as an optional first
argument to autodying C<system>:
system( [ 0, 1, 2 ], $cmd, @args); # 0,1,2 are good exit values
C<autodie> uses the L<IPC::System::Simple> module to change C<system>.
See its documentation for further information.
Applying C<autodie> to C<system> or C<exec> causes the exotic
forms C<system { $cmd } @args > or C<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 C<CORE::system>
or C<CORE::exec> instead, or use C<no autodie qw(system exec)> before
calling the exotic form.
=head1 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.
=head1 DIAGNOSTICS
=over 4
=item :void cannot be used with lexical scope
The C<:void> option is supported in L<Fatal>, but not
C<autodie>. To workaround this, C<autodie> may be explicitly disabled until
the end of the current block with C<no autodie>.
To disable autodie for only a single function (eg, open)
use C<no autodie qw(open)>.
C<autodie> performs no checking of called context to determine whether to throw
an exception; the explicitness of error handling with C<autodie> is a deliberate
feature.
=item No user hints defined for %s
You've insisted on hints for user-subroutines, either by pre-pending
a C<!> to the subroutine name itself, or earlier in the list of arguments
to C<autodie>. However the subroutine in question does not have
any hints available.
=back
See also L<Fatal/DIAGNOSTICS>.
=head1 BUGS
"Used only once" warnings can be generated when C<autodie> or C<Fatal>
is used with package filehandles (eg, C<FILE>). Scalar filehandles are
strongly recommended instead.
When using C<autodie> or C<Fatal> with user subroutines, the
declaration of those subroutines must appear before the first use of
C<Fatal> or C<autodie>, or have been exported from a module.
Attempting to use C<Fatal> or C<autodie> on other user subroutines will
result in a compile-time error.
Due to a bug in Perl, C<autodie> may "lose" any format which has the
same name as an autodying built-in or function.
C<autodie> may not work correctly if used inside a file with a
name that looks like a string eval, such as F<eval (3)>.
=head2 autodie and string eval
Due to the current implementation of C<autodie>, unexpected results
may be seen when used near or with the string version of eval.
I<None of these bugs exist when using block eval>.
Under Perl 5.8 only, C<autodie> I<does not> propagate into string C<eval>
statements, although it can be explicitly enabled inside a string
C<eval>.
Under Perl 5.10 only, using a string eval when C<autodie> is in
effect can cause the autodie behaviour to leak into the surrounding
scope. This can be worked around by using a C<no autodie> at the
end of the scope to explicitly remove autodie's effects, or by
avoiding the use of string eval.
I<None of these bugs exist when using block eval>. The use of
C<autodie> with block eval is considered good practice.
=head2 REPORTING BUGS
Please report bugs via the CPAN Request Tracker at
L<http://rt.cpan.org/NoAuth/Bugs.html?Dist=autodie>.
=head1 FEEDBACK
If you find this module useful, please consider rating it on the
CPAN Ratings service at
L<http://cpanratings.perl.org/rate?distribution=autodie> .
The module author loves to hear how C<autodie> has made your life
better (or worse). Feedback can be sent to
E<lt>pjf@perltraining.com.auE<gt>.
=head1 AUTHOR
Copyright 2008-2009, Paul Fenwick E<lt>pjf@perltraining.com.auE<gt>
=head1 LICENSE
This module is free software. You may distribute it under the
same terms as Perl itself.
=head1 SEE ALSO
L<Fatal>, L<autodie::exception>, L<autodie::hints>, L<IPC::System::Simple>
I<Perl tips, autodie> at
L<http://perltraining.com.au/tips/2008-08-20.html>
=head1 ACKNOWLEDGEMENTS
Mark Reed and Roland Giersig -- Klingon translators.
See the F<AUTHORS> file for full credits. The latest version of this
file can be found at
L<http://github.com/pfenwick/autodie/tree/master/AUTHORS> .
=cut