Determine whether a socket is at the out-of-band mark #include
<sys/socket.h> int sockatmark( int s ); - The file descriptor of
the socket that you want to check, as returned by socket(). Use
the -l socket option to qcc to link against this library. The
sockatmark() function determines whether the socket specified by
s is at the out-of-band data mark. If the protocol for the
socket supports out-of-band data by marking the stream with an
out-of-band data mark, sockatmark() returns 1 when all data
preceding the mark has been read and the out-of-band data mark
is the first element in the receive queue. The sockatmark()
function doesn't remove the out-of-band data mark from the
stream. Using this function between receive operations lets an
application determine which data comes before and after out-of-
band data. - The socket isn't at the out-of-band data mark. -
The socket is at the out-of-band data mark. - An error occurred
(errno is set). - Invalid file descriptor s. - The s argument
isn't the file descriptor o