SOCKATMARK(3) | Library Functions Manual | SOCKATMARK(3) |
sockatmark
—
determine whether the read pointer is at the OOB
mark
Standard C Library (libc, -lc)
#include
<sys/socket.h>
int
sockatmark
(int
s);
To find out if the read pointer is currently pointing at the mark
in the data stream, the
sockatmark
()
function is provided. If sockatmark
() returns 1, the
next read will return data after the mark. Otherwise (assuming out of band
data has arrived), the next read will provide data sent by the client prior
to transmission of the out of band signal. The routine used in the remote
login process to flush output on receipt of an interrupt or quit signal is
shown below. It reads the normal data up to the mark (to discard it), then
reads the out-of-band byte.
#include <sys/socket.h> ... oob() { int out = FWRITE, mark; char waste[BUFSIZ]; /* flush local terminal output */ ioctl(1, TIOCFLUSH, (char *)&out); for (;;) { if ((mark = sockatmark(rem)) < 0) { perror("sockatmark"); break; } if (mark) break; (void) read(rem, waste, sizeof (waste)); } if (recv(rem, &mark, 1, MSG_OOB) < 0) { perror("recv"); ... } ... }
Upon successful completion, the
sockatmark
() function returns the value 1 if the
read pointer is pointing at the OOB mark, 0 if it is not. Otherwise, the
value -1 is returned and the global variable errno is
set to indicate the error.
The sockatmark
() call fails if:
The sockatmark
() function was introduced
by IEEE Std 1003.1-2001 (“POSIX.1”),
to standardize the historical SIOCATMARK
ioctl(2). The
ENOTTY
error instead of the usual
ENOTSOCK
is to match the historical behavior of
SIOCATMARK
.
October 13, 2002 | macOS 14.6 |