The select system call can be used
with sockets to provide a synchronous multiplexing mechanism. The
system call has several parameters which govern its behavior. If
you specify a zero pointer for the timeout parameter timout,
select will block until one or
more of the specified socket descriptors is ready. If timout
is a non-zero pointer, it specifies a maximum interval to wait for
the selection to complete.
select is useful for datagram
socket descriptors to determine when data have arrived and are ready
to be read without blocking; use the FIONREAD parameter to the ioctl
system call to determine exactly how much data are available.
select for exceptional conditions
will return true for BSD sockets if out-of- band data is available.
select will always return true
for sockets which are no longer capable of being used (e.g. if a
close or shutdown
system call has been executed against them).
select is used in the same
way as in other applications. Refer to the select(2)
man page for information on how to use select.
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