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25 .TH SOCKATMARK 3 2008-12-03 "Linux" "Linux Programmer's Manual"
27 sockatmark \- determine whether socket is at out-of-band mark
29 .B #include <sys/socket.h>
31 .BI "int sockatmark(int " sockfd );
34 Feature Test Macro Requirements for glibc (see
35 .BR feature_test_macros (7)):
40 _POSIX_C_SOURCE\ >=\ 200112L || _XOPEN_SOURCE\ >=\ 600
44 returns a value indicating whether or not the socket referred
45 to by the file descriptor
47 is at the out-of-band mark.
48 If the socket is at the mark, then 1 is returned;
49 if the socket is not at the mark, 0 is returned.
50 This function does not remove the out-of-band mark.
54 returns 1 if the socket is at the out-of-band mark, or 0 if it is not.
55 On error, \-1 is returned and \fIerrno\fP is set to indicate the error.
60 is not a valid file descriptor.
63 .\" POSIX.1 says ENOTTY for this case
65 is not a file descriptor to which
70 was added to glibc in version 2.2.4.
76 returns 1, then the out-of-band data can be read using the
81 Out-of-band data is only supported on some stream socket protocols.
84 can safely be called from a handler for the
89 is implemented using the
98 The following code can be used after receipt of a
100 signal to read (and discard) all data up to the mark,
101 and then read the byte of data at the mark:
109 atmark = sockatmark(sockfd);
111 perror("sockatmark");
118 s = read(sockfd, buf, BUF_LEN) <= 0);
126 if (recv(sockfd, &oobdata, 1, MSG_OOB) == \-1) {