Comtrol eCos - Manual (Page 571)

Chapter 38. TCP/IP Library Reference
fd_set *fdsr;
int max = fd;
fdsr = (fd_set *)calloc(howmany(max+1, NFDBITS),
sizeof(fd_mask));
if (fdsr == NULL) {
...
return (-1);
}
FD_SET(fd, fdsr);
n = select(max+1, fdsr, NULL, NULL, &tv);
...
free(fdsr);
Alternatively, it is possible to use the poll(2) interface. poll(2) is
more efficient when the size of select()’s fd_set bit-arrays are very
large, and for fixed numbers of file descriptors one need not size and
dynamically allocate a memory object.
select() should probably have been designed to return the time remaining
from the original timeout, if any, by modifying the time value in place.
Even though some systems stupidly act in this different way, it is
unlikely this semantic will ever be commonly implemented, as the change
causes massive source code compatibility problems. Furthermore, recent
new standards have dictated the current behaviour. In general, due to
the existence of those brain-damaged non-conforming systems, it is unwise
to assume that the timeout value will be unmodified by the select() call,
and the caller should reinitialize it on each invocation. Calculating
the delta is easily done by calling gettimeofday(2) before and after the
call to select(), and using timersub() (as described in getitimer(2)).
Internally to the kernel, select() works poorly if multiple processes
wait on the same file descriptor. Given that, it is rather surprising to
see that many daemons are written that way (i.e., httpd(8)).
HISTORY
The select() function call appeared in 4.2BSD.
BSD March 25, 1994 BSD
send
SEND(2) System Calls Manual SEND(2)
NAME
send, sendto, sendmsg - send a message from a socket
SYNOPSIS
#include < sys/types.h>
#include < sys/socket.h>
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