On Fri, Apr 1, 2011 at 4:31 AM, Adriaan Renting <rent...@astron.nl> wrote: > L.S. > > I have a problem that a background process that I'm trying to start with > subprocess.Popen gets interrupted and starts waiting for input no matter > what I try to do to have it continue to run. It happens when I run it > with nohup in the background. > I've tried to find a solution searching the internet, but found none. > I've written a small test script that reproduces the problem and hope > maybe here there is someone who can tell me what's going wrong. Any > suggestions are welcome. > > (renting)myhost> cat test.py > #!/usr/bin/python > # script to test subprocess problem > import subprocess, sys, time > > for f in range(3): > command = ["ssh", "-T", "localhost", "uptime"] > comm = subprocess.Popen(command, shell=False, stdin=None, > stdout=subprocess.PIPE, stderr=subprocess.STDOUT, close_fds=True) > print '1' > if comm.returncode: > print "error: %i" % (comm.return_code) > else: > print '2' > (output, output2) = comm.communicate(input=None) > print output > print output2 > print '3' > time.sleep(3) > > (renting)myhost> python --version > Python 2.5.2 > > (renting)myhost> nohup ./test.py -O2 & > [1] 15679 > > (renting)myhost> 1 > 2 > 22:40:30 up 24 days, 7:32, 1 user, load average: 0.00, 0.00, 0.00 > > None > 3 > 1 > 2 > > [1] + Suspended (tty input) ./test.py -O2 > (renting)myhost> fg > ./test.py -O2 > > 22:40:35 up 24 days, 7:32, 1 user, load average: 0.00, 0.00, 0.00 > > None > 3 > 1 > 2 > 22:40:56 up 24 days, 7:32, 1 user, load average: 0.00, 0.00, 0.00 > > None > 3 > > (renting)myhost> > > Now as you can see, it suspends on the second time through the for loop, > until I bring it to the foreground and hit . > What you don't see, is that I make it do this by pushing the arrow keys > a couple of times. The same happens when I would exit the shell, despite > it running with nohup. > I don't need to exit to make it suspend, any combination of a few random > keystrokes makes it do this. It seems depending on the timing though, > during the sleep(3) it seems to ignore me, only when subprocess is > actually running will it suspend if I generate keystrokes. > If the ssh command is executed without -T option it suspends directly, > so I think it's related to the ssh command. I log in with a > public/private key pair to avoid having to enter a password. > > Any suggestions are welcome, >
What operating system is this? Try with stdin=open(os.devnull, 'rb') to the Popen call instead. Also, this seems to be similar: http://stackoverflow.com/questions/1365653/calling-fgets-on-popen-of-ssh-is-flushing-the-beginning-of-stdin-of-the-cal The "Suspended (tty input)" message means that a background process tried to read from stdin, so got suspended. This is part of the job control mechanism. -- regards, kushal -- http://mail.python.org/mailman/listinfo/python-list
