.\" Copyright (c) 1983, 1991 The Regents of the University of California. .\" All rights reserved. .\" .\" %%%LICENSE_START(BSD_4_CLAUSE_UCB) .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. All advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" This product includes software developed by the University of .\" California, Berkeley and its contributors. .\" 4. Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" %%%LICENSE_END .\" .\" $Id: getsockopt.2,v 1.1 1999/05/24 14:57:04 freitag Exp $ .\" .\" Modified Sat Jul 24 16:19:32 1993 by Rik Faith (faith@cs.unc.edu) .\" Modified Mon Apr 22 02:29:06 1996 by Martin Schulze (joey@infodrom.north.de) .\" Modified Tue Aug 27 10:52:51 1996 by Andries Brouwer (aeb@cwi.nl) .\" Modified Thu Jan 23 13:29:34 1997 by Andries Brouwer (aeb@cwi.nl) .\" Modified Sun Mar 28 21:26:46 1999 by Andries Brouwer (aeb@cwi.nl) .\" Modified 1999 by Andi Kleen . .\" Removed most stuff because it is in socket.7 now. .\" .TH GETSOCKOPT 2 2014-04-28 "Linux" "Linux Programmer's Manual" .SH NAME getsockopt, setsockopt \- get and set options on sockets .SH SYNOPSIS .nf .BR "#include " " /* See NOTES */" .br .B #include .sp .BI "int getsockopt(int " sockfd ", int " level ", int " optname , .BI " void *" optval ", socklen_t *" optlen ); .BI "int setsockopt(int " sockfd ", int " level ", int " optname , .BI " const void *" optval ", socklen_t " optlen ); .fi .SH DESCRIPTION .BR getsockopt () and .BR setsockopt () manipulate options for the socket referred to by the file descriptor .IR sockfd . Options may exist at multiple protocol levels; they are always present at the uppermost socket level. When manipulating socket options, the level at which the option resides and the name of the option must be specified. To manipulate options at the sockets API level, .I level is specified as .BR SOL_SOCKET . To manipulate options at any other level the protocol number of the appropriate protocol controlling the option is supplied. For example, to indicate that an option is to be interpreted by the .B TCP protocol, .I level should be set to the protocol number of .BR TCP ; see .BR getprotoent (3). The arguments .I optval and .I optlen are used to access option values for .BR setsockopt (). For .BR getsockopt () they identify a buffer in which the value for the requested option(s) are to be returned. For .BR getsockopt (), .I optlen is a value-result argument, initially containing the size of the buffer pointed to by .IR optval , and modified on return to indicate the actual size of the value returned. If no option value is to be supplied or returned, .I optval may be NULL. .I Optname and any specified options are passed uninterpreted to the appropriate protocol module for interpretation. The include file .I contains definitions for socket level options, described below. Options at other protocol levels vary in format and name; consult the appropriate entries in section 4 of the manual. Most socket-level options utilize an .I int argument for .IR optval . For .BR setsockopt (), the argument should be nonzero to enable a boolean option, or zero if the option is to be disabled. .PP For a description of the available socket options see .BR socket (7) and the appropriate protocol man pages. .SH RETURN VALUE On success, zero is returned. On error, \-1 is returned, and .I errno is set appropriately. .SH ERRORS .TP 10 .B EBADF The argument .I sockfd is not a valid descriptor. .TP .B EFAULT The address pointed to by .I optval is not in a valid part of the process address space. For .BR getsockopt (), this error may also be returned if .I optlen is not in a valid part of the process address space. .TP .B EINVAL .I optlen invalid in .BR setsockopt (). In some cases this error can also occur for an invalid value in .IR optval (e.g., for the .B IP_ADD_MEMBERSHIP option described in .BR ip (7)). .TP .B ENOPROTOOPT The option is unknown at the level indicated. .TP .B ENOTSOCK The argument .I sockfd is a file, not a socket. .SH CONFORMING TO SVr4, 4.4BSD (these system calls first appeared in 4.2BSD), POSIX.1-2001. .\" SVr4 documents additional ENOMEM and ENOSR error codes, but does .\" not document the .\" .BR SO_SNDLOWAT ", " SO_RCVLOWAT ", " SO_SNDTIMEO ", " SO_RCVTIMEO .\" options .SH NOTES POSIX.1-2001 does not require the inclusion of .IR , and this header file is not required on Linux. However, some historical (BSD) implementations required this header file, and portable applications are probably wise to include it. The .I optlen argument of .BR getsockopt () and .BR setsockopt () is in reality an .I "int [*]" (and this is what 4.x BSD and libc4 and libc5 have). Some POSIX confusion resulted in the present .IR socklen_t , also used by glibc. See also .BR accept (2). .SH BUGS Several of the socket options should be handled at lower levels of the system. .SH SEE ALSO .BR ioctl (2), .BR socket (2), .BR getprotoent (3), .BR protocols (5), .BR ip (7), .BR packet (7), .BR socket (7), .BR tcp (7), .BR udp (7), .BR unix (7) .SH COLOPHON This page is part of release 3.74 of the Linux .I man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at \%http://www.kernel.org/doc/man\-pages/.