On Jan 20, 9:19 am, srinivasan srinivas <[email protected]>
wrote:
> Do parent process will have different file descriptor in it for each
> subprocesses or paprent uses a single file descriptor for all?
> I really want to know creation of each subprocess will occupy an entry in
> parents'file descriptor table. B'cos if i create more than 200 subprocesses,
> i am getting 'Too many open files' error.
>
> Thanks,
> Srini
>
> ----- Original Message ----
> From: Mark Wooding <[email protected]>
> To: [email protected]
> Sent: Tuesday, 20 January, 2009 6:16:17 PM
> Subject: Re: Doubts related to subprocess.Popen()
>
> srinivasan srinivas <[email protected]> writes:
>
> > Does subprocess.Popen() count a new open file for each suprocess? I
> > mean does it occupy an entry in file descriptor table of parent
> > process? If so, wat is each file descriptor connected to?
>
> On Unix, subprocess.Popen will use up a file descriptor in the parent
> for each use of subprocess.PIPE. The descriptor in question is one end
> of a pipe; the child process holds the other end.
>
> I guess the situation is similar on Windows, but I don't know for sure.
>
> -- [mdw]
> --http://mail.python.org/mailman/listinfo/python-list
>
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Have you upped your open files limit? My test script:
import subprocess
procs = []
for i in xrange(400):
procs.append(subprocess.Popen("/bin/cat",
stdin=subprocess.PIPE, stdout=subprocess.PIPE,
stderr=subprocess.PIPE))
By default, 'ulimit -n' returns 1024, which is the number of open
files allowed. Running the test script without changing it results
in:
Traceback (most recent call last):
File "test.py", line 9, in <module>
stderr=subprocess.PIPE))
File "/usr/lib/python2.5/subprocess.py", line 593, in __init__
errread, errwrite)
File "/usr/lib/python2.5/subprocess.py", line 1002, in
_execute_child
errpipe_read, errpipe_write = os.pipe()
OSError: [Errno 24] Too many open files
Now, up that limit to 8192 via ulimit -n, and run the script again:
[r...@marvin jeff]# ulimit -n 8192
[r...@marvin jeff]# python test.py
[r...@marvin jeff]#
HTH,
Jeff
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