Open3 gives you access to stdin, stdout, and stderr when running other programs.


Add this line to your application's Gemfile:

gem 'open3'

And then execute:

$ bundle

Or install it yourself as:

$ gem install open3


Open3 grants you access to stdin, stdout, stderr and a thread to wait for the child process when running another program. You can specify various attributes, redirections, current directory, etc., of the program in the same way as for Process.spawn.

  • Open3.popen3 : pipes for stdin, stdout, stderr
  • Open3.popen2 : pipes for stdin, stdout
  • Open3.popen2e : pipes for stdin, merged stdout and stderr
  • Open3.capture3 : give a string for stdin; get strings for stdout, stderr
  • Open3.capture2 : give a string for stdin; get a string for stdout
  • Open3.capture2e : give a string for stdin; get a string for merged stdout and stderr
  • Open3.pipeline_rw : pipes for first stdin and last stdout of a pipeline
  • Open3.pipeline_r : pipe for last stdout of a pipeline
  • Open3.pipeline_w : pipe for first stdin of a pipeline
  • Open3.pipeline_start : run a pipeline without waiting
  • Open3.pipeline : run a pipeline and wait for its completion


After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to


Bug reports and pull requests are welcome on GitHub at