This library provides the fork, wait, wait2, waitpid, and waitpid2 methods
for MS Windows. In addition, it provides a different implementation of the
kill method, a proper implementation of Process.ppid, and decent analogues
of Process.getpriority, Process.setpriority, Process.getrlimit and


* windows-pr
* sys-proctable (dev only)
* test-unit 2 (dev only)

Supported Platforms

This library is supported on Windows 2000 or later.


gem install win32-process


require 'win32/process'

    puts 'In the child'
    sleep 1

puts 'Done'

Developer's Notes

The Process.fork and Process.wait methods

The fork method is emulated on Windows by spawning another Ruby process
against $PROGRAM_NAME via the CreateProcess() Win32 API function. It will
use its parent's environment and starting directory.

The various wait methods are a wrapper for the WaitForSingleObject() or
WaitForMultipleObjects() Win32 API functions, for the wait* and waitpid*
methods, respectively.  In the case of wait2 and waitpid2, the exit value
is returned via the GetExitCodeProcess() Win32API function.

For now the waitpid and waitpid2 calls do not accept a second argument.
That's because we haven't yet determined if there's a signal we should
allow to be sent.

Note that because fork is calling CreateProcess($PROGRAM_NAME), it will
start again from the top of the script instead of from the point of the
call. We will try to address this in a future release, if possible.

The Process.kill method

Initially, the kill method will try to get a HANDLE on the PID using the
OpenProcess() function. If that succeeds, we know the process is running.

In the event of signal 2 or signal 3, the GenerateConsoleCtrlEvent()
function is used to send a signal to that process. These will not kill
GUI processes. It will not (currently) send a signal to remote

In the event of signal 1 or 4-8, the CreateRemoteThread() function is used
after the HANDLE's process has been identified to create a thread
within that process. The ExitProcess() function is then sent to that

In the event of signal 9, the TerminateProcess() function is called. This
will almost certainly kill the process, but doesn't give the process a
chance to necessarily do any cleanup it might otherwise do.

The Process.ppid method

In MRI the Process.ppid always returns 0 on MS Windows. With this library
it returns the actual parent pid.

Differences between Ruby's kill and the Win32 Utils kill

Ruby does not currently use the CreateRemoteThread() + ExitProcess()
approach which is, according to everything I've read, a cleaner approach.
This includes not only online research but also Jeffrey Richter's
"Advanced Windows Programming, 3rd Edition."

Also, the way Process.kill handles multiple pids works slightly differently
(and better IMHO) in the Win32 Utils version than the way Ruby currently

The reason Process.kill was originally added, in case anyone cares for
historical trivia, is that Ruby 1.6.x did not support Process.kill on
Windows at all.


It is unlikely you will be able to kill system processes with this module.
It's probably better that you don't.

Known Bugs

None known (though please see the +Details+ section for quirks).  Any
bugs should be reported on the project page at

Future Plans

Train Process.fork to execute from the point of the call rather than the
top of the script (if possible).

Other suggestions welcome.


Artistic 2.0


(C) 2003-2011 Daniel J. Berger
All Rights Reserved


This library is provided "as is" and without any express or
implied warranties, including, without limitation, the implied
warranties of merchantability and fitness for a particular purpose.


Park Heesob	
Daniel J. Berger