/ 
IO-CaptureOutput-1.04_03
River stage two • 34 direct dependents • 62 total dependents
/ IO::CaptureOutput

NAME

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

VERSION

This documentation describes version 1.04_03.

SYNOPSIS

    use IO::CaptureOutput qw(capture capture_exec);

    my ($stdout, $stderr);

    sub noisy {
        warn "this sub prints to stdout and stderr!";
        print "arguments: @_";
    }

    capture sub {noisy(@args)}, \$stdout, \$stderr;

    ($stdout, $stderr) = capture_exec( 'perl', '-e', 
        'print "Hello"; print STDERR "World!"');

DESCRIPTION

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.

FUNCTIONS

The following functions will be exported on demand.

capture()

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.

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

@rv = capture(sub {wantarray}); # returns true
$rv = capture(sub {wantarray}); # returns defined, but not true
capture(sub {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.

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);

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

capture_exec()

($stdout, $stderr) = 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

    $stdout = capture_exec('perl', '-e', 'print "hello world"');

    ($stdout, $stderr) = 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 IPC::Open3.

You can check the exit status of the system() call with the $? variable. See perlvar for more information.

capture_exec_combined()

$combined = 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 and returns a single scalar.

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.

qxx()

This is an alias for capture_exec().

qxy()

This is an alias for capture_exec_combined().

SEE ALSO

AUTHORS

  • Simon Flack <simonflk _AT_ cpan.org> (original author)

  • David Golden <dagolden _AT_ cpan.org> (co-maintainer since version 1.04)

COPYRIGHT AND LICENSE

Portions copyright 2004, 2005 Simon Flack. Portions copyright 2007 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.