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.\" ========================================================================
.\"
.IX Title "autodie 3"
.TH autodie 3 "2013-02-22" "perl v5.16.3" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
autodie \- Replace functions with ones that succeed or die with lexical scope
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\&    use autodie;            # Recommended: implies \*(Aquse autodie qw(:default)\*(Aq
\&
\&    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\*(Aqt die
\&        open(my $fh, "<", $filename); # Could fail silently!
\&        no autodie;                   # disable all autodies
\&    }
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
.Vb 1
\&        bIlujDI\*(Aq yIchegh()Qo\*(Aq; yIHegh()!
\&
\&        It is better to die() than to return() in failure.
\&
\&                \-\- Klingon programming proverb.
.Ve
.PP
The \f(CW\*(C`autodie\*(C'\fR pragma provides a convenient way to replace functions
that normally return false on failure with equivalents that throw
an exception on failure.
.PP
The \f(CW\*(C`autodie\*(C'\fR pragma has \fIlexical scope\fR, meaning that functions
and subroutines altered with \f(CW\*(C`autodie\*(C'\fR will only change their behaviour
until the end of the enclosing block, file, or \f(CW\*(C`eval\*(C'\fR.
.PP
If \f(CW\*(C`system\*(C'\fR is specified as an argument to \f(CW\*(C`autodie\*(C'\fR, then it
uses IPC::System::Simple to do the heavy lifting.  See the
description of that module for more information.
.SH "EXCEPTIONS"
.IX Header "EXCEPTIONS"
Exceptions produced by the \f(CW\*(C`autodie\*(C'\fR pragma are members of the
autodie::exception class.  The preferred way to work with
these exceptions under Perl 5.10 is as follows:
.PP
.Vb 1
\&    use feature qw(switch);
\&
\&    eval {
\&        use autodie;
\&
\&        open(my $fh, \*(Aq<\*(Aq, $some_file);
\&
\&        my @records = <$fh>;
\&
\&        # Do things with @records...
\&
\&        close($fh);
\&
\&    };
\&
\&    given ($@) {
\&        when (undef)   { say "No error";                    }
\&        when (\*(Aqopen\*(Aq)  { say "Error from open";             }
\&        when (\*(Aq:io\*(Aq)   { say "Non\-open, IO error.";         }
\&        when (\*(Aq:all\*(Aq)  { say "All other autodie errors."    }
\&        default        { say "Not an autodie error at all." }
\&    }
.Ve
.PP
Under Perl 5.8, the \f(CW\*(C`given/when\*(C'\fR structure is not available, so the
following structure may be used:
.PP
.Vb 2
\&    eval {
\&        use autodie;
\&
\&        open(my $fh, \*(Aq<\*(Aq, $some_file);
\&
\&        my @records = <$fh>;
\&
\&        # Do things with @records...
\&
\&        close($fh);
\&    };
\&
\&    if ($@ and $@\->isa(\*(Aqautodie::exception\*(Aq)) {
\&        if ($@\->matches(\*(Aqopen\*(Aq)) { print "Error from open\en";   }
\&        if ($@\->matches(\*(Aq:io\*(Aq )) { print "Non\-open, IO error."; }
\&    } elsif ($@) {
\&        # A non\-autodie exception.
\&    }
.Ve
.PP
See autodie::exception for further information on interrogating
exceptions.
.SH "CATEGORIES"
.IX Header "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 \f(CW\*(C`:file\*(C'\fR will enable autodie for \f(CW\*(C`close\*(C'\fR, \f(CW\*(C`fcntl\*(C'\fR,
\&\f(CW\*(C`fileno\*(C'\fR, \f(CW\*(C`open\*(C'\fR and \f(CW\*(C`sysopen\*(C'\fR.
.PP
The categories are currently:
.PP
.Vb 10
\&    :all
\&        :default
\&            :io
\&                read
\&                seek
\&                sysread
\&                sysseek
\&                syswrite
\&                :dbm
\&                    dbmclose
\&                    dbmopen
\&                :file
\&                    binmode
\&                    close
\&                    chmod
\&                    chown
\&                    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
.Ve
.PP
Note that while the above category system is presently a strict
hierarchy, this should not be assumed.
.PP
A plain \f(CW\*(C`use autodie\*(C'\fR implies \f(CW\*(C`use autodie qw(:default)\*(C'\fR.  Note that
\&\f(CW\*(C`system\*(C'\fR and \f(CW\*(C`exec\*(C'\fR are not enabled by default.  \f(CW\*(C`system\*(C'\fR requires
the optional IPC::System::Simple module to be installed, and enabling
\&\f(CW\*(C`system\*(C'\fR or \f(CW\*(C`exec\*(C'\fR will invalidate their exotic forms.  See \*(L"\s-1BUGS\*(R"\s0
below for more details.
.PP
The syntax:
.PP
.Vb 1
\&    use autodie qw(:1.994);
.Ve
.PP
allows the \f(CW\*(C`:default\*(C'\fR 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 \f(CW\*(C`autodie\*(C'\fR module is
upgraded.
.PP
\&\f(CW\*(C`autodie\*(C'\fR can be enabled for all of Perl's built-ins, including
\&\f(CW\*(C`system\*(C'\fR and \f(CW\*(C`exec\*(C'\fR with:
.PP
.Vb 1
\&    use autodie qw(:all);
.Ve
.SH "FUNCTION SPECIFIC NOTES"
.IX Header "FUNCTION SPECIFIC NOTES"
.SS "flock"
.IX Subsection "flock"
It is not considered an error for \f(CW\*(C`flock\*(C'\fR to return false if it fails
due to an \f(CW\*(C`EWOULDBLOCK\*(C'\fR (or equivalent) condition.  This means one can
still use the common convention of testing the return value of
\&\f(CW\*(C`flock\*(C'\fR when called with the \f(CW\*(C`LOCK_NB\*(C'\fR option:
.PP
.Vb 1
\&    use autodie;
\&
\&    if ( flock($fh, LOCK_EX | LOCK_NB) ) {
\&        # We have a lock
\&    }
.Ve
.PP
Autodying \f(CW\*(C`flock\*(C'\fR will generate an exception if \f(CW\*(C`flock\*(C'\fR returns
false with any other error.
.SS "system/exec"
.IX Subsection "system/exec"
The \f(CW\*(C`system\*(C'\fR built-in is considered to have failed in the following
circumstances:
.IP "\(bu" 4
The command does not start.
.IP "\(bu" 4
The command is killed by a signal.
.IP "\(bu" 4
The command returns a non-zero exit value (but see below).
.PP
On success, the autodying form of \f(CW\*(C`system\*(C'\fR returns the \fIexit value\fR
rather than the contents of \f(CW$?\fR.
.PP
Additional allowable exit values can be supplied as an optional first
argument to autodying \f(CW\*(C`system\*(C'\fR:
.PP
.Vb 1
\&    system( [ 0, 1, 2 ], $cmd, @args);  # 0,1,2 are good exit values
.Ve
.PP
\&\f(CW\*(C`autodie\*(C'\fR uses the IPC::System::Simple module to change \f(CW\*(C`system\*(C'\fR.
See its documentation for further information.
.PP
Applying \f(CW\*(C`autodie\*(C'\fR to \f(CW\*(C`system\*(C'\fR or \f(CW\*(C`exec\*(C'\fR causes the exotic
forms \f(CW\*(C`system { $cmd } @args \*(C'\fR or \f(CW\*(C`exec { $cmd } @args\*(C'\fR
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 \f(CW\*(C`CORE::system\*(C'\fR
or \f(CW\*(C`CORE::exec\*(C'\fR instead, or use \f(CW\*(C`no autodie qw(system exec)\*(C'\fR before
calling the exotic form.
.SH "GOTCHAS"
.IX Header "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.
.SH "DIAGNOSTICS"
.IX Header "DIAGNOSTICS"
.IP ":void cannot be used with lexical scope" 4
.IX Item ":void cannot be used with lexical scope"
The \f(CW\*(C`:void\*(C'\fR option is supported in Fatal, but not
\&\f(CW\*(C`autodie\*(C'\fR.  To workaround this, \f(CW\*(C`autodie\*(C'\fR may be explicitly disabled until
the end of the current block with \f(CW\*(C`no autodie\*(C'\fR.
To disable autodie for only a single function (eg, open)
use \f(CW\*(C`no autodie qw(open)\*(C'\fR.
.Sp
\&\f(CW\*(C`autodie\*(C'\fR performs no checking of called context to determine whether to throw
an exception; the explicitness of error handling with \f(CW\*(C`autodie\*(C'\fR is a deliberate
feature.
.ie n .IP "No user hints defined for %s" 4
.el .IP "No user hints defined for \f(CW%s\fR" 4
.IX Item "No user hints defined for %s"
You've insisted on hints for user-subroutines, either by pre-pending
a \f(CW\*(C`!\*(C'\fR to the subroutine name itself, or earlier in the list of arguments
to \f(CW\*(C`autodie\*(C'\fR.  However the subroutine in question does not have
any hints available.
.PP
See also \*(L"\s-1DIAGNOSTICS\*(R"\s0 in Fatal.
.SH "BUGS"
.IX Header "BUGS"
\&\*(L"Used only once\*(R" warnings can be generated when \f(CW\*(C`autodie\*(C'\fR or \f(CW\*(C`Fatal\*(C'\fR
is used with package filehandles (eg, \f(CW\*(C`FILE\*(C'\fR).  Scalar filehandles are
strongly recommended instead.
.PP
When using \f(CW\*(C`autodie\*(C'\fR or \f(CW\*(C`Fatal\*(C'\fR with user subroutines, the
declaration of those subroutines must appear before the first use of
\&\f(CW\*(C`Fatal\*(C'\fR or \f(CW\*(C`autodie\*(C'\fR, or have been exported from a module.
Attempting to use \f(CW\*(C`Fatal\*(C'\fR or \f(CW\*(C`autodie\*(C'\fR on other user subroutines will
result in a compile-time error.
.PP
Due to a bug in Perl, \f(CW\*(C`autodie\*(C'\fR may \*(L"lose\*(R" any format which has the
same name as an autodying built-in or function.
.PP
\&\f(CW\*(C`autodie\*(C'\fR may not work correctly if used inside a file with a
name that looks like a string eval, such as \fIeval (3)\fR.
.SS "autodie and string eval"
.IX Subsection "autodie and string eval"
Due to the current implementation of \f(CW\*(C`autodie\*(C'\fR, unexpected results
may be seen when used near or with the string version of eval.
\&\fINone of these bugs exist when using block eval\fR.
.PP
Under Perl 5.8 only, \f(CW\*(C`autodie\*(C'\fR \fIdoes not\fR propagate into string \f(CW\*(C`eval\*(C'\fR
statements, although it can be explicitly enabled inside a string
\&\f(CW\*(C`eval\*(C'\fR.
.PP
Under Perl 5.10 only, using a string eval when \f(CW\*(C`autodie\*(C'\fR is in
effect can cause the autodie behaviour to leak into the surrounding
scope.  This can be worked around by using a \f(CW\*(C`no autodie\*(C'\fR at the
end of the scope to explicitly remove autodie's effects, or by
avoiding the use of string eval.
.PP
\&\fINone of these bugs exist when using block eval\fR.  The use of
\&\f(CW\*(C`autodie\*(C'\fR with block eval is considered good practice.
.SS "\s-1REPORTING BUGS\s0"
.IX Subsection "REPORTING BUGS"
Please report bugs via the \s-1CPAN\s0 Request Tracker at
<http://rt.cpan.org/NoAuth/Bugs.html?Dist=autodie>.
.SH "FEEDBACK"
.IX Header "FEEDBACK"
If you find this module useful, please consider rating it on the
\&\s-1CPAN\s0 Ratings service at
<http://cpanratings.perl.org/rate?distribution=autodie> .
.PP
The module author loves to hear how \f(CW\*(C`autodie\*(C'\fR has made your life
better (or worse).  Feedback can be sent to
<pjf@perltraining.com.au>.
.SH "AUTHOR"
.IX Header "AUTHOR"
Copyright 2008\-2009, Paul Fenwick <pjf@perltraining.com.au>
.SH "LICENSE"
.IX Header "LICENSE"
This module is free software.  You may distribute it under the
same terms as Perl itself.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
Fatal, autodie::exception, autodie::hints, IPC::System::Simple
.PP
\&\fIPerl tips, autodie\fR at
<http://perltraining.com.au/tips/2008\-08\-20.html>
.SH "ACKNOWLEDGEMENTS"
.IX Header "ACKNOWLEDGEMENTS"
Mark Reed and Roland Giersig \*(-- Klingon translators.
.PP
See the \fI\s-1AUTHORS\s0\fR file for full credits.  The latest version of this
file can be found at
<http://github.com/pfenwick/autodie/tree/master/AUTHORS> .
