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Groups > comp.lang.python > #91853

Re: fork/exec & close file descriptors

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Skip Montanaro <skip.montanaro@gmail.com> writes:

> Reviving (and concluding) a thread I started a couple weeks ago, I asked:
>
>> The basic fork/exec dance is not a problem, but how do I discover
>> all the open file descriptors in the new child process to make sure
>> they get closed? Do I simply start at fd 3 and call os.close() on
>> everything up to some largish fd number?
>
> I wanted this again today (for different reasons than before).
> Googling for "python close all file descriptors" returned the os
> module docs as the first hit, and lo and behold, what do I see
> documented? os.closerange (new in 2.6):
>
>     os.closerange(fd_low, fd_high)
>     Close all file descriptors from fd_low (inclusive) to fd_high
>     (exclusive), ignoring errors.

The close(2) manpage has the following warning on my Linux system:

| Not checking the return value of close() is a common  but  nevertheless
| serious  programming error.  It is quite possible that errors on a pre‐
| vious write(2) operation are first reported at the final close().   Not
| checking the return value when closing the file may lead to silent loss
| of data.  This can especially be observed with NFS and with disk quota.
| 

(I haven't followed the thread, but if your problem is to make sure fds
are closed on exec, you may be better off using the... close-on-exec
flag. Or simply do the bookkeeping.)

-- Alain.

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Re: fork/exec & close file descriptors Skip Montanaro <skip.montanaro@gmail.com> - 2015-06-02 08:58 -0500
  Re: fork/exec & close file descriptors Marko Rauhamaa <marko@pacujo.net> - 2015-06-02 18:28 +0300
    Re: fork/exec & close file descriptors Skip Montanaro <skip.montanaro@gmail.com> - 2015-06-02 10:42 -0500
      Re: fork/exec & close file descriptors Marko Rauhamaa <marko@pacujo.net> - 2015-06-02 19:24 +0300
        Re: fork/exec & close file descriptors Jon Ribbens <jon+usenet@unequivocal.co.uk> - 2015-06-02 16:37 +0000
    Re: fork/exec & close file descriptors MrJean1 <MrJean1@gmail.com> - 2015-06-12 13:43 -0700
  Re: fork/exec & close file descriptors Alain Ketterlin <alain@universite-de-strasbourg.fr.invalid> - 2015-06-02 17:59 +0200
    Re: fork/exec & close file descriptors Marko Rauhamaa <marko@pacujo.net> - 2015-06-02 23:05 +0300
      Re: fork/exec & close file descriptors Alain Ketterlin <alain@universite-de-strasbourg.fr.invalid> - 2015-06-02 23:06 +0200
        Re: fork/exec & close file descriptors Marko Rauhamaa <marko@pacujo.net> - 2015-06-03 01:24 +0300
          Re: fork/exec & close file descriptors Alain Ketterlin <alain@universite-de-strasbourg.fr.invalid> - 2015-06-03 09:21 +0200
            Re: fork/exec & close file descriptors Marko Rauhamaa <marko@pacujo.net> - 2015-06-03 10:41 +0300
              Re: fork/exec & close file descriptors alister <alister.nospam.ware@ntlworld.com> - 2015-06-03 09:38 +0000
                Re: fork/exec & close file descriptors Steven D'Aprano <steve@pearwood.info> - 2015-06-03 22:07 +1000
                Re: fork/exec & close file descriptors alister <alister.nospam.ware@ntlworld.com> - 2015-06-03 12:18 +0000
                Re: fork/exec & close file descriptors Marko Rauhamaa <marko@pacujo.net> - 2015-06-03 15:27 +0300
                Re: fork/exec & close file descriptors alister <alister.nospam.ware@ntlworld.com> - 2015-06-03 13:05 +0000
                Re: fork/exec & close file descriptors Marko Rauhamaa <marko@pacujo.net> - 2015-06-03 17:49 +0300
                Re: fork/exec & close file descriptors Marko Rauhamaa <marko@pacujo.net> - 2015-06-03 15:25 +0300
                Re: fork/exec & close file descriptors random832@fastmail.us - 2015-06-03 08:54 -0400
                Re: fork/exec & close file descriptors Marko Rauhamaa <marko@pacujo.net> - 2015-06-03 16:08 +0300
                Re: fork/exec & close file descriptors random832@fastmail.us - 2015-06-03 09:21 -0400
                Re: fork/exec & close file descriptors Chris Angelico <rosuav@gmail.com> - 2015-06-03 23:32 +1000
                Re: fork/exec & close file descriptors Marko Rauhamaa <marko@pacujo.net> - 2015-06-03 16:33 +0300
                Re: fork/exec & close file descriptors Marko Rauhamaa <marko@pacujo.net> - 2015-06-03 17:43 +0300
                Re: fork/exec & close file descriptors random832@fastmail.us - 2015-06-03 16:08 -0400
                Re: fork/exec & close file descriptors Marko Rauhamaa <marko@pacujo.net> - 2015-06-04 00:09 +0300
                Re: fork/exec & close file descriptors random832@fastmail.us - 2015-06-03 16:07 -0400
                Re: fork/exec & close file descriptors Chris Angelico <rosuav@gmail.com> - 2015-06-04 07:54 +1000
        Re: fork/exec & close file descriptors Chris Angelico <rosuav@gmail.com> - 2015-06-03 09:54 +1000
          Re: fork/exec & close file descriptors Alain Ketterlin <alain@universite-de-strasbourg.fr.invalid> - 2015-06-03 09:11 +0200
            Re: fork/exec & close file descriptors random832@fastmail.us - 2015-06-03 08:21 -0400
              Re: fork/exec & close file descriptors Alain Ketterlin <alain@universite-de-strasbourg.fr.invalid> - 2015-06-03 15:16 +0200
        Re: fork/exec & close file descriptors Skip Montanaro <skip.montanaro@gmail.com> - 2015-06-02 20:21 -0500

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