select.2 (2010 09)

select(2) select(2)

for (k=0; k < NWORDS; k++)

readmask.fds_bits[k] = 0;

for (i=0, k=0; i < NTTYS && k < NWORDS; k++)

for (j=0; j < NFDBITS && i < NTTYS; j++, i++) {

ttymask[i] = MASK(tty[i]);

readmask.fds_bits[k] |= ttymask[i];

}

timeout.tv_sec = 5;

timeout.tv_usec = 0;

for (k=0; k < NWORDS; k++)

readfds.fds_bits[k] = readmask.fds_bits[k];

/* select on NTTYS+3 file descriptors if stdin, stdout

* and stderr are also open

if ((nfound = select (NTTYS+3, &readfds, 0, 0, &timeout)) == -1)

perror ("select failed");

else if (nfound == 0)

printf ("select timed out \n");

else for (i=0, k=0; i < NTTYS && k < NWORDS; k++)

for (j=0; j < NFDBITS && i < NTTYS; j++, i++)

if (ttymask[i] & readfds.fds_bits[k])

/* Read from tty[i]. The code for reading

* is not shown here.

else printf ("tty[%d] is not ready for reading \n",i);

WARNINGS

The ﬁle descriptor masks are always modiﬁed on return, even if the call returns as the result of a

timeout.

DEPENDENCIES

select() supports the following devices and ﬁle types:

• pipes

• ﬁfo special ﬁles (named pipes)

• all serial devices

• All ITEs (internal terminal emulators) and HP-HIL input devices

• lan (7) special ﬁles

• pty (7) special ﬁles

• sockets

AUTHOR

select() was developed by HP and the University of California, Berkeley.