Re: close_range?

> Linux and FreeBSD have adopted a syscall close_range(min, max, flags)
> that, depending on flags, either closes, marks cloexec, or `unshares'
> every file descriptor d with min <= d <= max.

> [...] (I'll ignore `unshare' for now which does not really have
> first-class semantics in NetBSD anyway.) [...]

What _are_ its semantics?  Based on the name, my reaction would be to
expect that either (a) it's got something to do with threading and/or
Linuxish clone(CLONE_FILES), decoupling one thread/process's fd from
another's, or (b) something akin to dup but happening at the open file
table level instead of the file descriptor level.

I don't like the close_range() name, because it sometimes has nothing
to do with closing (the unshare option).  I also see no need for
burning another syscall number; I'd prefer to make those fcntl()
operations, either with more than three arguments or with the third arg
being a pointer to a struct.

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