fork/exec & close file descriptors

[random832 at fastmail.us]

On Wed, Jun 3, 2015, at 03:11, Alain Ketterlin wrote:
> Thank you, I know this. What I mean is: what are the reasons that you
> cannot access your file descriptors one by one? To me closing a range of
> descriptors has absolutely no meaning, simply because ranges have no
> meaning for file descriptors (they're not ordered in any way). What if
> some library uses its own descriptors that happen to lie in your
> "range"? Etc.

The context in which this is useful is that you've just forked, and
you're about to exec. "Some library" isn't going to ever get back
control within the current process. Generally the range of file
descriptors you want to close is (e.g.) 3-Infinity, after you've already
got 0 1 and 2 pointing to where you want them (whatever redirected file
or pipe).