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    IO::CaptureOutput - capture STDOUT and STDERR from Perl code,
    subprocesses or XS

    This documentation describes version 1.1101.

         use IO::CaptureOutput qw(capture qxx qxy);
     # STDOUT and STDERR separately
         capture { noisy_sub(@args) } \$stdout, \$stderr;
     # STDOUT and STDERR together
         capture { noisy_sub(@args) } \$combined, \$combined;
     # STDOUT and STDERR from external command
         ($stdout, $stderr, $success) = qxx( @cmd );
     # STDOUT and STDERR together from external command
         ($combined, $success) = qxy( @cmd );

    This module provides routines for capturing STDOUT and STDERR from perl
    subroutines, forked system calls (e.g. "system()", "fork()") and from XS
    or C modules.

    The following functions will be exported on demand.

         capture \&subroutine, \$stdout, \$stderr;

    Captures everything printed to "STDOUT" and "STDERR" for the duration of
    &subroutine. $stdout and $stderr are optional scalars that will contain
    "STDOUT" and "STDERR" respectively.

    "capture()" uses a code prototype so the first argument can be specified
    directly within brackets if desired.

         # shorthand with prototype
         capture { print __PACKAGE__ } \$stdout, \$stderr;

    Returns the return value(s) of &subroutine. The sub is called in the
    same context as "capture()" was called e.g.:

         @rv = capture { wantarray } ; # returns true
         $rv = capture { wantarray } ; # returns defined, but not true
         capture { wantarray };       # void, returns undef

    "capture()" is able to capture output from subprocesses and C code,
    which traditional "tie()" methods of output capture are unable to do.

    Note: "capture()" will only capture output that has been written or
    flushed to the filehandle.

    If the two scalar references refer to the same scalar, then "STDERR"
    will be merged to "STDOUT" before capturing and the scalar will hold the
    combined output of both.

         capture \&subroutine, \$combined, \$combined;

    Normally, "capture()" uses anonymous, temporary files for capturing
    output. If desired, specific file names may be provided instead as
    additional options.

         capture \&subroutine, \$stdout, \$stderr, $out_file, $err_file;

    Files provided will be clobbered, overwriting any previous data, but
    will persist after the call to "capture()" for inspection or other

    By default, when no references are provided to hold STDOUT or STDERR,
    output is captured and silently discarded.

         # Capture STDOUT, discard STDERR
         capture \&subroutine, \$stdout;
     # Discard STDOUT, capture STDERR
         capture \&subroutine, undef, \$stderr;

    However, even when using "undef", output can be captured to specific

         # Capture STDOUT to a specific file, discard STDERR
         capture \&subroutine, \$stdout, undef, $outfile;
     # Discard STDOUT, capture STDERR to a specific file
         capture \&subroutine, undef, \$stderr, undef, $err_file;
     # Discard both, capture merged output to a specific file
         capture \&subroutine, undef, undef, $mergedfile;

    It is a fatal error to merge STDOUT and STDERR and request separate,
    specific files for capture.

         # ERROR:
         capture \&subroutine, \$stdout, \$stdout, $out_file, $err_file;
         capture \&subroutine, undef, undef, $out_file, $err_file;

    If either STDOUT or STDERR should be passed through to the terminal
    instead of captured, provide a reference to undef -- "\undef" -- instead
    of a capture variable.

         # Capture STDOUT, display STDERR
         capture \&subroutine, \$stdout, \undef;
     # Display STDOUT, capture STDERR
         capture \&subroutine, \undef, \$stderr;

         ($stdout, $stderr, $success, $exit_code) = capture_exec(@args);

    Captures and returns the output from "system(@args)". In scalar context,
    "capture_exec()" will return what was printed to "STDOUT". In list
    context, it returns what was printed to "STDOUT" and "STDERR" as well as
    a success flag and the exit value.

         $stdout = capture_exec('perl', '-e', 'print "hello world"');
     ($stdout, $stderr, $success, $exit_code) = 
             capture_exec('perl', '-e', 'warn "Test"');

    "capture_exec" passes its arguments to "system()" and on MSWin32 will
    protect arguments with shell quotes if necessary. This makes it a handy
    and slightly more portable alternative to backticks, piped "open()" and

    The $success flag returned will be true if the command ran successfully
    and false if it did not (if the command could not be run or if it ran
    and returned a non-zero exit value). On failure, the raw exit value of
    the "system()" call is available both in the $exit_code returned and in
    the $? variable.

       ($stdout, $stderr, $success, $exit_code) = 
           capture_exec('perl', '-e', 'warn "Test" and exit 1');
   if ( ! $success ) {
           print "The exit code was " . ($exit_code >> 8) . "\n";

    See perlvar for more information on interpreting a child process exit

         ($combined, $success, $exit_code) = capture_exec_combined(
             'perl', '-e', 'print "hello\n"', 'warn "Test\n"

    This is just like "capture_exec()", except that it merges "STDERR" with
    "STDOUT" before capturing output.

    Note: there is no guarantee that text printed to "STDOUT" and "STDERR"
    in the subprocess will be appear in order. The actual order will depend
    on how IO buffering is handled in the subprocess.

    This is an alias for "capture_exec()".

    This is an alias for "capture_exec_combined()".

    *   IPC::Open3

    *   IO::Capture

    *   IO::Utils

    *   IPC::System::Simple

    *   Simon Flack <simonflk _AT_> (original author)

    *   David Golden <dagolden _AT_> (co-maintainer since version

    Portions copyright 2004, 2005 Simon Flack. Portions copyright 2007, 2008
    David Golden. All rights reserved.

    You may distribute under the terms of either the GNU General Public
    License or the Artistic License, as specified in the Perl README file.

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