Re: How to increse [sic.] max open files?

Matthias Urlichs (
7 Jan 1997 03:20:33 +0100

In, article <5andlm$>, (H. Peter Anvin) writes:
> By author: (yuri mironoff)
> >
> > Forgive my ignorance but why not implement dynamic file descriptor
> > allocation??? All these arguments about a maximum NR_OPEN would then
> > become inconsequential.
> It ain't so easy, and it's BSD's fault. select() has a very nice way
> to ensure that a bitmask of file descriptors is the right size, but
> the FD_* support routines immediately bungles that very nice idea by
> effectively requiring the maximum number of file descriptors
> (technically, the largest possible numerical value of a file
> descriptor) to be known at compile time. There is no way in C to

This is the kernel mailing list. The first step is to fix the kernel,
including 2.0.27+, to support "unlimited" fd_sets. This hasn't happened
yet. (Somebody said he's working on this..?)

After that has happened, we can think about application programs.
Most programs won't ever open more files than the default FD_SETSIZE.
Those that do should just define a reasonable maximum they can handle,
or allocate the fd_set buffers themselves (it's not that difficult even if
you don't use C++).

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