This gem aims at being a simple and reliable solution for controlling external programs running in the background on any Ruby / OS combination.

The code originated in the selenium-webdriver gem, but should prove useful as a standalone library.

Build Status


process ="ruby", "-e", "sleep")

# inherit stdout/stderr from parent...!

# ...or pass an IO ="child-output")

# start the process


# check process status
process.alive?    #=> true
process.exited?   #=> false

# wait indefinitely for process to exit...
process.exited?   #=> true

# ...or poll for exit + force quit
rescue ChildProcess::TimeoutError
  process.stop # tries increasingly harsher methods to kill the process.

The object returned from will implement ChildProcess::AbstractProcess.


How the process is launched and killed depends on the platform:

  • Unix : fork + exec (or posix_spawn if enabled)
  • Windows : CreateProcess and friends
  • JRuby : java.lang.Process,ProcessBuilder

Note on Patches/Pull Requests

  • Fork the project.
  • Make your feature addition or bug fix.
  • Add tests for it. This is important so I don't break it in a future version unintentionally.
  • Commit, do not mess with rakefile, version, or history. (if you want to have your own version, that is fine but bump version in a commit by itself I can ignore when I pull)
  • Send me a pull request. Bonus points for topic branches.


Copyright (c) 2010-2012 Jari Bakken. See LICENSE for details.