# Generated by Pod::WikiDoc version 0.18

=pod

=head1 NAME

Capture::Tiny - Capture STDOUT and STDERR from Perl, XS or external programs

=head1 VERSION

This documentation describes version 0.06.

=head1 SYNOPSIS

     use Capture::Tiny qw/capture tee capture_merged tee_merged/;
 
     ($stdout, $stderr) = capture {
       # your code here
     };
 
     ($stdout, $stderr) = tee {
       # your code here
     };
 
     $merged = capture_merged {
       # your code here
     };
 
     $merged = tee_merged {
       # your code here
     };

=head1 DESCRIPTION

Capture::Tiny provides a simple, portable way to capture anything sent to
STDOUT or STDERR, regardless of whether it comes from Perl, from XS code or
from an external program.  Optionally, output can be teed so that it is
captured while being passed through to the original handles.  Yes, it even
works on Windows.  Stop guessing which of a dozen capturing modules to use in
any particular situation and just use this one.

This module was heavily inspired by L<IO::CaptureOutput>, which provides
similar functionality without the ability to tee output and with more
complicated code and API.

=head1 USAGE

The following functions are available.  None are exported by default.

=head2 capture

   ($stdout, $stderr) = capture \&code;
   $stdout = capture \&code;

The C<<< capture >>> function takes a code reference and returns what is sent to
STDOUT and STDERR.  In scalar context, it returns only STDOUT.  If no output
was received, returns an empty string.  Regardless of context, all output is
captured -- nothing is passed to the existing handles.

It is prototyped to take a subroutine reference as an argument. Thus, it
can be called in block form:

   ($stdout, $stderr) = capture {
     # your code here ...
   };

=head2 capture_merged

   $merged = capture_merged \&code;

The C<<< capture_merged >>> function works just like C<<< capture >>> except STDOUT and
STDERR are merged. (Technically, STDERR is redirected to STDOUT before
executing the function.)  If no output was received, returns an empty string.
As with C<<< capture >>> it may be called in block form.

Caution: STDOUT and STDERR output in the merged result are not guaranteed to be
properly ordered due to buffering.

=head2 tee

   ($stdout, $stderr) = tee \&code;
   $stdout = tee \&code;

The C<<< tee >>> function works just like C<<< capture >>>, except that output is captured
as well as passed on to the original STDOUT and STDERR.  As with C<<< capture >>> it
may be called in block form.

=head2 tee_merged

   $merged = tee_merged \&code;

The C<<< tee_merged >>> function works just like C<<< capture_merged >>> except that output
is captured as well as passed on to STDOUT.  As with C<<< capture >>> it may be called
in block form.

Caution: STDOUT and STDERR output in the merged result are not guaranteed to be
properly ordered due to buffering.

=head1 LIMITATIONS

=head2 Portability

Portability is a goal, not a guarantee.  C<<< tee >>> requires fork, except on
Windows where C<<< system(1, @cmd) >>> is used instead.  Not tested on any
particularly esoteric platforms yet.

=head2 PerlIO layers

Capture::Tiny does it's best to preserve PerlIO layers such as ':utf8' or
':crlf' when capturing.   Layers should be applied to STDOUT or STDERR I<before>
the call to C<<< capture >>> or C<<< tee >>>.

=head2 Closed STDIN, STDOUT or STDERR

Capture::Tiny will work even if STDIN, STDOUT or STDERR have been previously
closed.  However, since they may be reopened to capture or tee output, any code
within the captured block that depends on finding them closed will, of course,
not find them to be closed.  If they started closed, Capture::Tiny will reclose
them again when the capture block finishes.

=head2 Scalar filehandles and STDIN, STDOUT or STDERR

If STDOUT or STDERR are reopened to scalar filehandles prior to the call to
C<<< capture >>> or C<<< tee >>>, then Capture::Tiny will override the output handle for the
duration of the C<<< capture >>> or C<<< tee >>> call and then send captured output to the
output handle after the capture is complete.  (Requires Perl 5.8)

Capture::Tiny attempts to preserve the semantics of STDIN opened to a scalar
reference.

=head2 Tied STDIN, STDOUT or STDERR

If STDOUT or STDERR are tied prior to the call to C<<< capture >>> or C<<< tee >>>, then
Capture::Tiny will attempt to override the tie for the duration of the
C<<< capture >>> or C<<< tee >>> call and then send captured output to the tied handle after
the capture is complete.  (Requires Perl 5.8)

Capture::Tiny does not (yet) support resending utf8 encoded data to a tied
STDOUT or STDERR handle.  Characters will appear as bytes.

Capture::Tiny attempts to preserve the semantics of tied STDIN, but capturing
or teeing when STDIN is tied is currently broken on Windows.

=head2 Modifiying STDIN, STDOUT or STDERR during a capture

Attempting to modify STDIN, STDOUT or STDERR I<during> C<<< capture >>> or C<<< tee >>> is
almost certainly going to cause problems.  Don't do that.

=head1 BUGS

Please report any bugs or feature requests using the CPAN Request Tracker.
Bugs can be submitted through the web interface at
L<http://rt.cpan.org/Dist/Display.html?Queue=Capture-Tiny>

When submitting a bug or request, please include a test-file or a patch to an
existing test-file that illustrates the bug or desired feature.

=head1 SEE ALSO

This is a selection of CPAN modules that provide some sort of output capture,
albeit with various limitations that make them appropriate only in particular
circumstances.  I'm probably missing some.  The long list is provided to show
why I felt Capture::Tiny was necessary.

=over

=item *

L<IO::Capture>

=item *

L<IO::Capture::Extended>

=item *

L<IO::CaptureOutput>

=item *

L<IPC::Capture>

=item *

L<IPC::Cmd>

=item *

L<IPC::Open2>

=item *

L<IPC::Open3>

=item *

L<IPC::Open3::Simple>

=item *

L<IPC::Open3::Utils>

=item *

L<IPC::Run>

=item *

L<IPC::Run::SafeHandles>

=item *

L<IPC::Run::Simple>

=item *

L<IPC::Run3>

=item *

L<IPC::System::Simple>

=item *

L<Tee>

=item *

L<IO::Tee>

=item *

L<File::Tee>

=item *

L<Filter::Handle>

=item *

L<Tie::STDERR>

=item *

L<Tie::STDOUT>

=item *

L<Test::Output>

=back

=head1 AUTHOR

David A. Golden (DAGOLDEN)

=head1 COPYRIGHT AND LICENSE

Copyright (c) 2009 by David A. Golden. All rights reserved.

Licensed under Apache License, Version 2.0 (the "License").  You may not use
this file except in compliance with the License.  A copy of the License was
distributed with this file or you may obtain a copy of the License from
http:E<sol>E<sol>www.apache.orgE<sol>licensesE<sol>LICENSE-2.0

Files produced as output though the use of this software, shall not be
considered Derivative Works, but shall be considered the original work of the
Licensor.

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.


