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Revision as of 15:06, 24 November 2009 by Jamesboston (talk | contribs) (News and Progress)
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Name of Project



Replace the existing nsIProcess interface with new interface that:

  • supports Unicode on all platforms
  • supports piping to and from processes
  • can handle asynchronous I/O via callbacks
  • is available through Components.utils.import("resource://gre/process.js") or a similar JS module approach.



James Boston


Steve Lee


Mark Finkle, Benjamin Smedberg, Ted Mielczarek, Jason Orendorff, David Humphrey

News and updates


All posts are tagged 'nsIProcess':

Or an RSS feed of the same:

News and Progress

(Click dates for attachments or info)

Sept 21, 2008: A first draft (an alpha version really) of the API is posted.

Sept 22, 2008: Released an updated version of an extension that serves as a temporary work around for nsIProcess bugs.

Sept 25, 2008: Submitted patch to bugzilla.

Oct 3, 2008: Submitted revised patch to bugzilla.

Oct 12, 2008: Opened a bug on NSPR lack of unicode support for Unicode arguments.

Nov 11, 2008: Submitted a new patch to bugzilla with Unicode support for Windows.

Nov 23, 2008: Submitted a new patch to bugzilla with isRunning() method.

Jan 25, 2009: Submitted a new patch with unit tests.

Mar 5, 2009: Submitted a new patch with minor revisions. The bug has now also been marked blocking‑fennec.

Mar 9, 2009: Changed interface to return void on run.

Mar 12, 2009: Patch pushed to mozilla-central. (Followed by a minor bustage fix.)

Mar 19, 2009: Filed a new enhancement bug that ties together the various features in the next stage of development.


The code will be done in trunk. To get changeset:

hg pull

Or to generate a plain text patch file containing all deviations from trunk visit:


The API for nsIProcess is not fully implemented. At present, the PID of a created process is not retained and cannot be killed. The API would also benifit from a new spec that includes inter-process communication.

An example of an API that for creating processes and communicating with them through STDIN/STDOUT is the Python subprocess module:

The goal of this project is to create a similar API for Mozilla.

API proposal

Existing API

Code snippet of how to use the existing API

Existing Code

Relevant bugs

Implement a replacement for nsIProcess

nsIProcess.kill() does not work on Win32

Implement inter-process communication (IPC) in Mozilla

PR_CreateProcess in NSPR needs unicode support

Submitted patches

Bug 442393 patches: Patches submitted to fix Bug 442393 - nsIProcess.kill() does not work on Win32

Meetings (Chronological)

Sept 19, 2008: Discussion with Benjamin Smedberg and David Humphrey to discuss the new API proposal.

Sept 22, 2008: Discussion with Mark Finkle and David Humphrey about the API design.

Sept 23, 2008: Discussion with Mark Finkle about using NSPR.

Oct 8, 2008: Discussion about string types and Windows paths in NSPR.

Oct 29, 2008: Advice regarding PRProcess type.

Nov 5, 2008: Getting advice on callbacks across XPConnect divide.

Nov 7, 2008: Round table on Unicode support.

Nov 23, 2008: Discussion about pathnames in xpcshell.