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29 .Nd determine whether the read pointer is at the OOB mark
35 .Fn sockatmark "int s"
37 To find out if the read pointer is currently pointing at
38 the mark in the data stream, the
43 returns 1, the next read will return data
45 Otherwise (assuming out of band data has arrived),
46 the next read will provide data sent by the client prior
47 to transmission of the out of band signal.
49 in the remote login process to flush output on receipt of an
50 interrupt or quit signal is shown below.
51 It reads the normal data up to the mark (to discard it),
52 then reads the out-of-band byte.
53 .Bd -literal -offset indent
54 #include <sys/socket.h>
58 int out = FWRITE, mark;
61 /* flush local terminal output */
62 ioctl(1, TIOCFLUSH, (char *)&out);
64 if ((mark = sockatmark(rem)) < 0) {
70 (void) read(rem, waste, sizeof (waste));
72 if (recv(rem, &mark, 1, MSG_OOB) < 0) {
80 Upon successful completion, the
82 function returns the value 1 if the read pointer is pointing at
83 the OOB mark, 0 if it is not.
84 Otherwise the value \-1 is returned
85 and the global variable
98 is not a valid descriptor.
103 is a descriptor for a file, not a socket.
109 .%T "An Introductory 4.4BSD Interprocess Communication Tutorial"
112 .%U https://docs.freebsd.org/44doc/psd/20.ipctut/paper.pdf
114 .%T "An Advanced 4.4BSD Interprocess Communication Tutorial"
115 .%A Samuel J. Leffler
121 .%U https://docs.freebsd.org/44doc/psd/21.ipc/paper.pdf
126 function was introduced by
128 to standardize the historical
133 error instead of the usual
135 is to match the historical behavior of