Joe Kutner created JRUBY-6362:
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Summary: Subprocess IO yields no ouput
Key: JRUBY-6362
URL: https://jira.codehaus.org/browse/JRUBY-6362
Project: JRuby
Issue Type: Bug
Reporter: Joe Kutner
Assignee: Thomas E Enebo
Attachments: subprocess.rb
While trying to fix a JRuby specific bug in Vagrant <http://vagrantup.com/>
that uses
ChildProcess (<https://github.com/jarib/childprocess>) to execute some
commands, I found that output cannot always be retrieved from a subprocess.
I've been able to reproduce the bug in a single file here:
https://gist.github.com/1647275
It is creating two ChildProcesses (via the Subprocess class), and executing
them in order.
Vagrant::Util::Subprocess.new("VBoxManage", "--version").execute
Vagrant::Util::Subprocess.new("VBoxManage", "--version").execute
In the execute method, a ChildProcess is created:
process = ChildProcess.build(*@command)
stdout, stdout_writer = IO.pipe
stderr, stderr_writer = IO.pipe
process.io.stdout = stdout_writer
process.io.stderr = stderr_writer
process.duplex = true
Then it tried to read the output from the stdout pipe:
data << io.read_nonblock(READ_CHUNK_SIZE)
The first time, the ChildProcess works correctly, but the second time it
yields no output.
INFO subprocess: Starting process: ["VBoxManage", "--version"]
DEBUG subprocess: Selecting on IO
DEBUG subprocess: stdout: 4.1.8r75467
DEBUG subprocess: Waiting for process to exit. Remaining to timeout: 32000
DEBUG subprocess: Exit status: 0
INFO subprocess: Starting process: ["VBoxManage", "--version"]
DEBUG subprocess: Selecting on IO
DEBUG subprocess: Waiting for process to exit. Remaining to timeout: 31999
DEBUG subprocess: Exit status: 0
Reproduce with this script:
https://gist.github.com/1647275
Background:
http://markmail.org/thread/e7rmwy4jp53e3wjj
https://github.com/mitchellh/vagrant/issues/658
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