1GETSOCKOPT(3P) POSIX Programmer's Manual GETSOCKOPT(3P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
12 getsockopt — get the socket options
13
15 #include <sys/socket.h>
16 int getsockopt(int socket, int level, int option_name,
18 void *restrict option_value, socklen_t *restrict option_len);
19
21 The getsockopt() function manipulates options associated with a socket.
22 The getsockopt() function shall retrieve the value for the option spec‐
24 ified by the option_name argument for the socket specified by the
25 socket argument. If the size of the option value is greater than
26 option_len, the value stored in the object pointed to by the
27 option_value argument shall be silently truncated. Otherwise, the
28 object pointed to by the option_len argument shall be modified to indi‐
29 cate the actual length of the value.
30 The level argument specifies the protocol level at which the option
32 resides. To retrieve options at the socket level, specify the level
33 argument as SOL_SOCKET. To retrieve options at other levels, supply the
34 appropriate level identifier for the protocol controlling the option.
35 For example, to indicate that an option is interpreted by the TCP
36 (Transmission Control Protocol), set level to IPPROTO_TCP as defined in
37 the <netinet/in.h> header.
38 The socket in use may require the process to have appropriate privi‐
40 leges to use the getsockopt() function.
41 The option_name argument specifies a single option to be retrieved. It
43 can be one of the socket-level options defined in <sys_socket.h> and
44 described in Section 2.10.16, Use of Options.
45
47 Upon successful completion, getsockopt() shall return 0; otherwise, -1
48 shall be returned and errno set to indicate the error.
49
51 The getsockopt() function shall fail if:
52 EBADF The socket argument is not a valid file descriptor.
54 EINVAL The specified option is invalid at the specified socket level.
56 ENOPROTOOPT
58 The option is not supported by the protocol.
59 ENOTSOCK
61 The socket argument does not refer to a socket.
62 The getsockopt() function may fail if:
64 EACCES The calling process does not have appropriate privileges.
66 EINVAL The socket has been shut down.
68 ENOBUFS
70 Insufficient resources are available in the system to complete
71 the function.
72 The following sections are informative.
74
76 None.
77
79 None.
80
82 None.
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85 None.
86
88 Section 2.10.16, Use of Options, bind(), close(), endprotoent(), set‐
89 sockopt(), socket()
90 The Base Definitions volume of POSIX.1‐2017, <sys_socket.h>,
92 <netinet_in.h>
93
95 Portions of this text are reprinted and reproduced in electronic form
96 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
97 table Operating System Interface (POSIX), The Open Group Base Specifi‐
98 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
99 Electrical and Electronics Engineers, Inc and The Open Group. In the
100 event of any discrepancy between this version and the original IEEE and
101 The Open Group Standard, the original IEEE and The Open Group Standard
102 is the referee document. The original Standard can be obtained online
103 at http://www.opengroup.org/unix/online.html .
104 Any typographical or formatting errors that appear in this page are
106 most likely to have been introduced during the conversion of the source
107 files to man page format. To report such errors, see https://www.ker‐
108 nel.org/doc/man-pages/reporting_bugs.html .
109IEEE/The Open Group 2017 GETSOCKOPT(3P)