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From: Marko Rauhamaa <marko@pacujo.net>
Newsgroups: comp.lang.python
Subject: Re: fork/exec & close file descriptors
Date: Wed, 03 Jun 2015 17:49:23 +0300
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alister <alister.nospam.ware@ntlworld.com>:

> I meant the program that is supplying your app with file handles
> willy- nilly without caring what happens to them

You seem to be advocating a strategy whereby the application keeps close
track of all file descriptors and closes them individually as needed.

Thing is, processes can be forked by library calls. For example, you
might have developed a class that converts a synchronous database API
into an asynchronous one. You'll have your object fork a helper process
that makes blocking calls while the object methods make sure never to
block the caller.

The application doesn't know the library would be starting a child
process. On the other hand, the library has no idea on what files the
application might have open. That's why the library traverses all file
descriptors and closes them categorically after forking.


Marko