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Groups > comp.lang.python > #91907

Re: fork/exec & close file descriptors

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Alain Ketterlin <alain@universite-de-strasbourg.fr.invalid>:

> Marko Rauhamaa <marko@pacujo.net> writes:
>> First, if close() fails, what's a poor program to do?
>
> Warn the user? Not assume everything went well? It all depends on the
> application, and what the file descriptor represents.

The problem here is in the system call contract, which is broken.
There's no fix. The man page admonition is just hand-waving without
constructive advice.

>> Try again?
> Could be a good idea on NFS or other kind of mounts.

Maybe close() will fail for ever.

> I can't imagine why one would like to mass-close an arbitrary set of
> file descriptors,

That's standard practice before execking a file. Failure to do that can
seriously hurt the parent process. For example, the parent (or child)
will never read an EOF from file descriptor if its duplicate is open in
an unwitting child process. Also, the number of open files in the system
may grow over all limits or simply waste kernel resources.

Close-on-exec is nice, maybe. However, you don't have control over all
file descriptors. Loggers, high-level library calls and others open
files without the application programmer knowing or having direct
control over.

> and I think APIs like os.closerange() are toxic and an appeal to
> sloppy programming.

And you recommend what instead?


Marko

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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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