Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages


home | help
IO::Capture::Stderr(3)User Contributed Perl DocumentatioIO::Capture::Stderr(3)

       "IO::Capture::Stderr" - Capture all output sent to "STDERR"

	   use IO::Capture::Stderr;

	   $capture = IO::Capture::Stderr->new();

	   $capture->start();	       # STDERR	Output captured
	   print STDERR	"Test Line One\n";
	   print STDERR	"Test Line Two\n";
	   print STDERR	"Test Line Three\n";
	   $capture->stop();	       # STDERR	output sent to wherever	it was before 'start'

	   # In	'scalar	context' returns next line
	   $line = $capture->read;
	   print "$line";	  # prints "Test Line One"

	   $line = $capture->read;
	   print "$line";	  # prints "Test Line Two"

	   # move line pointer to line 1

	   $line = $capture->read;
	   print "$line";	  # prints "Test Line One"

	   # Find out current line number
	   $current_line_position = $capture->line_pointer;

	   # In	'List Context' return an array(list)
	   @all_lines =	$capture->read;

	   # Example 1 - "Using	in module tests"
	   #  Note: If you don't want to make users install
	   #	    the	IO::Capture module just	for your tests,
	   #	    you	can just install in the	t/lib directory
	   #	    of your module and use the lib pragma in
	   #	    your tests.

	   use lib "t/lib";
	   use IO::Capture:Stderr;

	   use Test::More;

	       # Create	new capture object.  Showing FORCE_CAPTURE_WARN	being cleared
	       # for example, but 0 is the default, so you don't need to specify
	       # unless	you want to set.
	   my $capture =  IO::Capture:Stderr->new( {FORCE_CAPTURE_WARN => 0} );

	   # execute with a bad	parameter to make sure get
	   # an	error.

	   ok( ! $test("Bad Parameter")	);


       The module "IO::Capture::Stderr", is derived from the abstract class
       "IO::Capture".  See IO::Capture.	The purpose of the module (as the name
       suggests) is to capture any output sent to "STDOUT".  After the capture
       is stopped, the STDOUT filehandle will be reset to the previous
       location. E.g., If previously redirected	to a file, when
       "IO::Capture->stop" is called, output will start	going into that	file

       Note:  This module won't	work with the perl function, system(), or any
       other operation
	      involving	a fork().  If you want to capture the output from a
       system command,
	      it is faster to use open() or back-ticks.

	      my $output = `/usr/sbin/ls -l 2>&1`;

       o   Creates a new capture object.

       o   An object can be reused as needed, so will only need	to do one of

	   o   Be aware, any data previously captured will be discarded	if a
	       new capture session is started.

       o   Start capturing data	into the "IO::Capture" Object.

       o   Can not be called on	an object that is already capturing.

       o   Can not be called while STDERR tied to an object.

       o   "undef" will	be returned on an error.

       o   Stop	capturing data and point STDERR	back to	it's previous output
	   location I.e., untie	STDERR

       o   In Scalar Context

	   o   Lines are read from the buffer at the position of the
	       "line_pointer", and the pointer is incremented by one.

		   $next_line =	$capture->read;

       o   In List Context

	   o   The array is returned.  The "line_pointer" is not affected.

		   @buffer = $capture->read;

       o   Data	lines are returned exactly as they were	captured.  You may
	   want	to use "chomp" on them if you don't want the end of line

	       while (my $line = $capture->read) {
		   chomp $line;
		   $cat_line = join '',	$cat_line, $line;

       o   Reads or sets the "line_pointer".

	       my $current_line	= $capture->line_pointer;

       Pass any	arguments to new() in a	single array reference.

	  IO::Capture::Stderr->new( {FORCE_CAPTURE_WARN	=> 1} );

	   Normally, IO::Capture::Stderr will capture text from	warn()
	   function calls. This	is because output from warn() is normally
	   directed to STDERR.	If you wish to force IO::Capture::Stderr to
	   grab	the text from warn(), set FORCE_CAPTURE_WARN to	a 1.  Then
	   "IO::Capture::Stderr" will save the handle that $SIG{__WARN__} was
	   set to, redirect it to itself on "start()", and then	set
	   $SIG{__WARN__} back after "stop()" is called.

   Adding Features
       If you would like to sub-class this module to add a feature (method) or
       two, here is a couple of	easy steps. Also see IO::Capture::Overview.

       1.  Give	your package a name

	       package MyPackage;

       2.  Use this "IO::Capture::Stderr" as your base class like this:

	       package MyPackage;

	       use base	qw/IO::Capture::Stderr/;

       3.  Add your new	method like this

	       package MyPackage;

	       use base	qw/IO::Capture::Stderr/;

	       sub grep	{
		   my $self = shift;

		   for $line (

See Also



       Mark Reynolds

       Jon Morgan

       Copyright (c) 2003, Mark	Reynolds. All Rights Reserved.	This module is
       free software. It may be	used, redistributed and/or modified under the
       same terms as Perl itself.

perl v5.32.1			  2005-04-30		IO::Capture::Stderr(3)


Want to link to this manual page? Use this URL:

home | help