1 .\" Copyright (c) 1983, 1991 The Regents of the University of California.
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32 .\" $Id: getsockopt.2,v 1.1 1999/05/24 14:57:04 freitag Exp $
34 .\" Modified Sat Jul 24 16:19:32 1993 by Rik Faith (faith@cs.unc.edu)
35 .\" Modified Mon Apr 22 02:29:06 1996 by Martin Schulze (joey@infodrom.north.de)
36 .\" Modified Tue Aug 27 10:52:51 1996 by Andries Brouwer (aeb@cwi.nl)
37 .\" Modified Thu Jan 23 13:29:34 1997 by Andries Brouwer (aeb@cwi.nl)
38 .\" Modified Sun Mar 28 21:26:46 1999 by Andries Brouwer (aeb@cwi.nl)
39 .\" Modified 1999 by Andi Kleen <ak@muc.de>.
40 .\" Removed most stuff because it is in socket.7 now.
42 .TH GETSOCKOPT 2 2008-12-03 "Linux" "Linux Programmer's Manual"
44 getsockopt, setsockopt \- get and set options on sockets
47 .BR "#include <sys/types.h>" " /* See NOTES */"
49 .B #include <sys/socket.h>
51 .BI "int getsockopt(int " sockfd ", int " level ", int " optname ,
52 .BI " void *" optval ", socklen_t *" optlen );
53 .BI "int setsockopt(int " sockfd ", int " level ", int " optname ,
54 .BI " const void *" optval ", socklen_t " optlen );
60 manipulate options for the socket referred to by the file descriptor
62 Options may exist at multiple
63 protocol levels; they are always present at the uppermost
66 When manipulating socket options, the level at which the
67 option resides and the name of the option must be specified.
68 To manipulate options at the sockets API level,
72 To manipulate options at any
73 other level the protocol number of the appropriate protocol
74 controlling the option is supplied.
76 to indicate that an option is to be interpreted by the
80 should be set to the protocol number of
89 are used to access option values for
93 they identify a buffer in which the value for the
94 requested option(s) are to be returned.
98 is a value-result argument, initially containing the
99 size of the buffer pointed to by
101 and modified on return to indicate the actual size of
103 If no option value is to be supplied or returned,
108 and any specified options are passed uninterpreted to the appropriate
109 protocol module for interpretation.
112 contains definitions for socket level options, described below.
114 other protocol levels vary in format and name; consult the appropriate
115 entries in section 4 of the manual.
117 Most socket-level options utilize an
123 the argument should be nonzero to enable a boolean option, or zero if the
124 option is to be disabled.
126 For a description of the available socket options see
128 and the appropriate protocol man pages.
130 On success, zero is returned.
131 On error, \-1 is returned, and
133 is set appropriately.
139 is not a valid descriptor.
142 The address pointed to by
144 is not in a valid part of the process address space.
147 this error may also be returned if
149 is not in a valid part of the process address space.
155 In some cases this error can also occur for an invalid value in
163 The option is unknown at the level indicated.
168 is a file, not a socket.
170 SVr4, 4.4BSD (these system calls first appeared in 4.2BSD),
172 .\" SVr4 documents additional ENOMEM and ENOSR error codes, but does
174 .\" .BR SO_SNDLOWAT ", " SO_RCVLOWAT ", " SO_SNDTIMEO ", " SO_RCVTIMEO
177 POSIX.1-2001 does not require the inclusion of
179 and this header file is not required on Linux.
180 However, some historical (BSD) implementations required this header
181 file, and portable applications are probably wise to include it.
191 (and this is what 4.x BSD and libc4 and libc5 have).
192 Some POSIX confusion resulted in the present
198 Several of the socket options should be handled at lower levels of the