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23 .TH SOCKATMARK 3 2008-12-03 "Linux" "Linux Programmer's Manual"
25 sockatmark \- determine whether socket is at out-of-band mark
27 .B #include <sys/socket.h>
29 .BI "int sockatmark(int " sockfd );
32 Feature Test Macro Requirements for glibc (see
33 .BR feature_test_macros (7)):
38 _POSIX_C_SOURCE\ >=\ 200112L || _XOPEN_SOURCE\ >=\ 600
42 returns a value indicating whether or not the socket referred
43 to by the file descriptor
45 is at the out-of-band mark.
46 If the socket is at the mark, then 1 is returned;
47 if the socket is not at the mark, 0 is returned.
48 This function does not remove the out-of-band mark.
52 returns 1 if the socket is at the out-of-band mark, or 0 if it is not.
53 On error, \-1 is returned and \fIerrno\fP is set to indicate the error.
58 is not a valid file descriptor.
61 .\" POSIX.1 says ENOTTY for this case
63 is not a file descriptor to which
68 was added to glibc in version 2.2.4.
74 returns 1, then the out-of-band data can be read using the
79 Out-of-band data is only supported on some stream socket protocols.
82 can safely be called from a handler for the
87 is implemented using the
96 The following code can be used after receipt of a
98 signal to read (and discard) all data up to the mark,
99 and then read the byte of data at the mark:
107 atmark = sockatmark(sockfd);
109 perror("sockatmark");
116 s = read(sockfd, buf, BUF_LEN) <= 0);
124 if (recv(sockfd, &oobdata, 1, MSG_OOB) == \-1) {