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

VERSION
    version 0.16

SYNOPSIS
       use Capture::Tiny ':all';
 
       ($stdout, $stderr, @result) = capture {
         # your code here
       };
 
       $stdout = capture_stdout { ... };
       $stderr = capture_stderr { ... };
       $merged = capture_merged { ... };
 
       ($stdout, $stderr) = tee {
         # your code here
       };
 
       $stdout = tee_stdout { ... };
       $stderr = tee_stderr { ... };
       $merged = tee_merged { ... };

DESCRIPTION
    Capture::Tiny provides a simple, portable way to capture almost 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 (usually). Stop guessing which of a dozen
    capturing modules to use in any particular situation and just use this
    one.

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

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

    The "capture" function takes a code reference and returns what is sent
    to STDOUT and STDERR as well as any return values from the code
    reference. In scalar context, it returns only STDOUT. If no output was
    received for a handle, it returns an empty string for that handle.
    Regardless of calling 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 ...
       };

    Note that the coderef is evaluated in list context. If you wish to force
    scalar context on the return value, you must use the "scalar" keyword.

       ($stdout, $stderr, $count) = capture {
         my @list = qw/one two three/;
         return scalar @list; # $count will be 3
       };

    Captures are normally done internally to an anonymous filehandle. To
    capture via a named file (e.g. to externally monitor a long-running
    capture), provide custom filehandles as a trailing list of option pairs:

       my $out_fh = IO::File->new("out.txt", "w+");
       my $err_fh = IO::File->new("out.txt", "w+");
       capture { ... } stdout => $out_fh, stderr => $err_fh;

    The filehandles must be read/write and seekable. Modifying the files or
    filehandles during a capture operation will give unpredictable results.
    Existing IO layers on them may be changed by the capture.

  capture_stdout
       ($stdout, @result) = capture_stdout \&code;
       $stdout = capture_stdout \&code;

    The "capture_stdout" function works just like "capture" except only
    STDOUT is captured. STDERR is not captured.

  capture_stderr
       ($stderr, @result) = capture_stderr \&code;
       $stderr = capture_stderr \&code;

    The "capture_stderr" function works just like "capture" except only
    STDERR is captured. STDOUT is not captured.

  capture_merged
       ($merged, @result) = capture_merged \&code;
       $merged = capture_merged \&code;

    The "capture_merged" function works just like "capture" except STDOUT
    and STDERR are merged. (Technically, STDERR is redirected to STDOUT
    before executing the function.)

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

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

    The "tee" function works just like "capture", except that output is
    captured as well as passed on to the original STDOUT and STDERR.

  tee_stdout
       ($stdout, @result) = tee_stdout \&code;
       $stdout = tee_stdout \&code;

    The "tee_stdout" function works just like "tee" except only STDOUT is
    teed. STDERR is not teed (output goes to STDERR as usual).

  tee_stderr
       ($stderr, @result) = tee_stderr \&code;
       $stderr = tee_stderr \&code;

    The "tee_stderr" function works just like "tee" except only STDERR is
    teed. STDOUT is not teed (output goes to STDOUT as usual).

  tee_merged
       ($merged, @result) = tee_merged \&code;
       $merged = tee_merged \&code;

    The "tee_merged" function works just like "capture_merged" except that
    output is captured as well as passed on to STDOUT.

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

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

  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
    *before* the call to "capture" or "tee". This may not work for tied
    handles (see below).

  Modifying filehandles before capturing
    Generally speaking, you should do little or no manipulation of the
    standard IO handles prior to using Capture::Tiny. In particular,
    closing, reopening, localizing or tying standard handles prior to
    capture may cause a variety of unexpected, undesirable and/or unreliable
    behaviors, as described below. Capture::Tiny does its best to compensate
    for these situations, but the results may not be what you desire.

    Closed filehandles

    Capture::Tiny will work even if STDIN, STDOUT or STDERR have been
    previously closed. However, since they will 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 close them again when the capture block
    finishes.

    Note that this reopening will happen even for STDIN or a handle not
    being captured to ensure that the filehandle used for capture is not
    opened to file descriptor 0, as this causes problems on various
    platforms.

    Localized filehandles

    If code localizes any of Perl's standard handles before capturing, the
    capture will affect the localized handles and not the original ones.
    External system calls are not affected by localizing a handle in Perl
    and will continue to send output to the original handles (which will
    thus not be captured).

    Scalar filehandles

    If STDOUT or STDERR are reopened to scalar filehandles prior to the call
    to "capture" or "tee", then Capture::Tiny will override the output
    handle for the duration of the "capture" or "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.

    Tied output handles

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

    Capture::Tiny may not succeed resending UTF-8 encoded data to a tied
    STDOUT or STDERR handle. Characters may appear as bytes. If the tied
    handle is based on Tie::StdHandle, then Capture::Tiny will attempt to
    determine appropriate layers like ":utf8" from the underlying handle and
    do the right thing.

    Tied input handle

    Capture::Tiny attempts to preserve the semantics of tied STDIN, but this
    is not entirely stable or portable. For example:

    *   Capturing or teeing with STDIN tied is broken on Windows

    *   FCGI has been reported as having a pathological tied handle
        implementation that causes fatal (and hard to diagnose) errors

    Unless having STDIN tied is crucial, it may be safest to localize STDIN
    when capturing:

       my ($out, $err) = do { local *STDIN; capture { ... } };

  Modifying handles during a capture
    Attempting to modify STDIN, STDOUT or STDERR *during* "capture" or "tee"
    is almost certainly going to cause problems. Don't do that.

  No support for Perl 5.8.0
    It's just too buggy when it comes to layers and UTF-8.

ENVIRONMENT
  PERL_CAPTURE_TINY_TIMEOUT
    Capture::Tiny uses subprocesses for "tee". By default, Capture::Tiny
    will timeout with an error if the subprocesses are not ready to receive
    data within 30 seconds (or whatever is the value of
    $Capture::Tiny::TIMEOUT). An alternate timeout may be specified by
    setting the "PERL_CAPTURE_TINY_TIMEOUT" environment variable. Setting it
    to zero will disable timeouts.

BUGS
    Please report any bugs or feature requests using the CPAN Request
    Tracker. Bugs can be submitted through the web interface at
    <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.

SEE ALSO
    This module was, inspired by IO::CaptureOutput, which provides similar
    functionality without the ability to tee output and with more
    complicated code and API. IO::CaptureOutput does not handle layers or
    most of the unusual cases described in the "Limitations" section and I
    no longer recommend it.

    There are many other 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.

    *   IO::Capture

    *   IO::Capture::Extended

    *   IO::CaptureOutput

    *   IPC::Capture

    *   IPC::Cmd

    *   IPC::Open2

    *   IPC::Open3

    *   IPC::Open3::Simple

    *   IPC::Open3::Utils

    *   IPC::Run

    *   IPC::Run::SafeHandles

    *   IPC::Run::Simple

    *   IPC::Run3

    *   IPC::System::Simple

    *   Tee

    *   IO::Tee

    *   File::Tee

    *   Filter::Handle

    *   Tie::STDERR

    *   Tie::STDOUT

    *   Test::Output

SUPPORT
  Bugs / Feature Requests
    Please report any bugs or feature requests through the issue tracker at
    <http://rt.cpan.org/Public/Dist/Display.html?Name=Capture-Tiny>. You
    will be notified automatically of any progress on your issue.

  Source Code
    This is open source software. The code repository is available for
    public review and contribution under the terms of the license.

    <https://github.com/dagolden/capture-tiny>

      git clone https://github.com/dagolden/capture-tiny.git

AUTHOR
    David Golden <dagolden@cpan.org>

COPYRIGHT AND LICENSE
    This software is Copyright (c) 2009 by David Golden.

    This is free software, licensed under:

      The Apache License, Version 2.0, January 2004

