Open3 does not capture stdout on Jruby

Summary

When using Open3#capture2 in Jruby in tests run through Travis, stdout is not captured and is instead printed to the log. This happens for all of the Open3 methods: catpure2, capture3, and open2/3. However, running a system command using backticks correctly captures output.

Travis environment:

  • dist: xenial
  • rvm:
    • jruby-9.1 (uses 9.1.17)
    • jruby-9.2 (uses 9.2.5.0)

Example build with the issue: https://travis-ci.org/github/aws/aws-sdk-ruby/jobs/700939400

Test code:

      raw_out, process_status = Open3.capture2('echo "Hello"')
      puts "cap2: #{raw_out}"  # hello is printed directly to the logs.  raw_out is empty"

      raw_out, process_status = Open3.capture2e('echo "Hello"')
      puts "cap2e: #{raw_out}" # hello is printed directly to the logs.  raw_out is empty"

      raw_out, process_status = Open3.capture2e('echo "Hello"', binmode: true)
      puts "cap2e, binmode: #{raw_out}" # nothing printed to the logs.  raw_out is empty"

      raw_out = `echo "Hello"`
      puts "backticks: #{raw_out}"  # nothing printed in logs. raw_out is set to hello
1 Like

Is this not a JRuby bug?

I don’t think it is - testing locally with identical versions of Jruby, Open3 behaves as expected (also tested using docker w/ travisci/ubuntu-ruby:18.04).

I also tested it via SSH – ok, too. Must be something special in how specifically Travis implements standard streams. Without knowing that, can’t say anything else.

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