exceptfds in select(2)
Michael Garzione
garzione at convex.com
Fri Mar 23 02:55:00 AEST 1990
The form of select(2) is
nfound = select(nfds, readfds, writefds, exceptfds, timeout)
int nfound, nfds;
fd_set *readfds, *writefds, *exceptfds;
struct timeval *timeout;
The only references to "exceptfds" I can find say that it "indicates
if an exceptional condition is pending" (man page); "indicates when exceptional
conditions exist for particular file descriptors, useful in networking"
(Bach); and misc. discussions about reading and writing (Leffler et. al.)
My guess is that the appropriate bit in exceptfds is set when the i/o
channel associated with a descriptor is lost, or in the case of some
sockets, out of band data is present (or maybe that would be readfds?).
Does anyone know for sure what a set bit in exceptfds indicates (what an
"exceptional condition" is)?
Mike Garzione
Convex Computer Corporation
{uunet,sun}!convex!garzione
garzione at convex.com
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