Python subprocess hangs if trying to read its output

Question

I have this little utility function that I use to execute external processes. In some cases, it hangs when I try to read the output of the process. Commenting out the output reading lines, it works.

def execute(command, cwd):
    command = command.split(' ')
    process = Popen(command,
        stderr=STDOUT, stdout=PIPE,
        cwd = cwd)

    # WITHOUT THIS IT WORKS
    #for line in process.stdout:    
    #    log.info('executing %s for user %s: %s' % (command, user.username, line))

    # ANOTHER TRY AT READING THE OUTPUT. ALSO MAKES IT HANG
    #output = p.communicate()[0]
    #log.info('executing %s for user %s: %s' % (command, user.username, output))

    process.wait()

Any help? I need to output for debugging purpose.

What is the command you are trying to execute? Also, to parse a command, use `shlex.split(command)` to ensure handling of quotes and such. — Martijn Pieters, Sep 25 '12 at 08:03
see http://stackoverflow.com/questions/2804543/read-subprocess-stdout-line-by-line — georg, Sep 25 '12 at 09:11

score 2 · Answer 1 · answered Sep 25 '12 at 08:12

2

I started using async_subprocess years ago and never looked back. It's also available from PyPI here.

answered Sep 25 '12 at 08:12

Nicola Musatti

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Python subprocess hangs if trying to read its output

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