没有标准输出的启动过程

Question

I am using a python script as a bootstrapper to start a long running java service.

call = [ "java", "-cp", ... ]

with open(os.devnull, 'w') as fnull:
    subprocess.Popen(call, stdout=fnull)
    print "Service started."

But when the python process has finished, I am still getting stdout output from the java process. I assume this is because python has shut my fnull so it reverts back to normal stdout.

How can I achieve what I want?

EDIT: On a side note, it would be nice to still get stderr if at all possible, but not if it adds any complexity.

EDIT2: It would appear that I am very much a moron, it was stderr that was being written to.

Answer 1

Partial answer to the side note, its easy to get stderr (its more complex when you want both stdout and stderr). It has the added advantage that it will tell you whether the java output you think is on stdout is really on stderr.

call = [ "java", "-cp", ... ]

with open(os.devnull, 'w') as fnull:
    subprocess.Popen(call, stdout=fnull, stderr=subprocess.PIPE)
    print "Service started."
for line in stderr:
    print 'stderr: ', line.strip()

Answer 2

If you are okay with letting the python script live

Popen.communicate(input=None)

Interact with process: Send data to stdin. Read data from stdout and stderr, until end-of-file is reached. Wait for process to terminate. The optional input argument should be a string to be sent to the child process, or None, if no data should be sent to the child.