mirror of https://github.com/mkerrisk/man-pages
208 lines
6.4 KiB
Groff
208 lines
6.4 KiB
Groff
.\" Copyright (c) 1983, 1991 The Regents of the University of California.
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $Id: getsockopt.2,v 1.1 1999/05/24 14:57:04 freitag Exp $
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.\"
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.\" Modified Sat Jul 24 16:19:32 1993 by Rik Faith (faith@cs.unc.edu)
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.\" Modified Mon Apr 22 02:29:06 1996 by Martin Schulze (joey@infodrom.north.de)
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.\" Modified Tue Aug 27 10:52:51 1996 by Andries Brouwer (aeb@cwi.nl)
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.\" Modified Thu Jan 23 13:29:34 1997 by Andries Brouwer (aeb@cwi.nl)
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.\" Modified Sun Mar 28 21:26:46 1999 by Andries Brouwer (aeb@cwi.nl)
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.\" Modified 1999 by Andi Kleen <ak@muc.de>.
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.\" Removed most stuff because it is in socket.7 now.
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.\"
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.TH GETSOCKOPT 2 2008-12-03 "Linux" "Linux Programmer's Manual"
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.SH NAME
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getsockopt, setsockopt \- get and set options on sockets
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.SH SYNOPSIS
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.nf
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.BR "#include <sys/types.h>" " /* See NOTES */"
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.br
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.B #include <sys/socket.h>
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.sp
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.BI "int getsockopt(int " sockfd ", int " level ", int " optname ,
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.BI " void *" optval ", socklen_t *" optlen );
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.BI "int setsockopt(int " sockfd ", int " level ", int " optname ,
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.BI " const void *" optval ", socklen_t " optlen );
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.fi
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.SH DESCRIPTION
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.BR getsockopt ()
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and
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.BR setsockopt ()
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manipulate options for the socket referred to by the file descriptor
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.IR sockfd .
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Options may exist at multiple
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protocol levels; they are always present at the uppermost
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socket level.
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When manipulating socket options, the level at which the
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option resides and the name of the option must be specified.
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To manipulate options at the sockets API level,
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.I level
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is specified as
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.BR SOL_SOCKET .
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To manipulate options at any
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other level the protocol number of the appropriate protocol
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controlling the option is supplied.
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For example,
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to indicate that an option is to be interpreted by the
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.B TCP
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protocol,
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.I level
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should be set to the protocol number of
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.BR TCP ;
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see
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.BR getprotoent (3).
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The arguments
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.I optval
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and
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.I optlen
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are used to access option values for
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.BR setsockopt ().
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For
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.BR getsockopt ()
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they identify a buffer in which the value for the
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requested option(s) are to be returned.
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For
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.BR getsockopt (),
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.I optlen
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is a value-result argument, initially containing the
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size of the buffer pointed to by
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.IR optval ,
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and modified on return to indicate the actual size of
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the value returned.
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If no option value is to be supplied or returned,
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.I optval
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may be NULL.
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.I Optname
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and any specified options are passed uninterpreted to the appropriate
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protocol module for interpretation.
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The include file
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.I <sys/socket.h>
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contains definitions for socket level options, described below.
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Options at
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other protocol levels vary in format and name; consult the appropriate
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entries in section 4 of the manual.
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Most socket-level options utilize an
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.I int
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argument for
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.IR optval .
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For
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.BR setsockopt (),
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the argument should be nonzero to enable a boolean option, or zero if the
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option is to be disabled.
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.PP
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For a description of the available socket options see
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.BR socket (7)
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and the appropriate protocol man pages.
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.SH "RETURN VALUE"
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On success, zero is returned.
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On error, \-1 is returned, and
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.I errno
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is set appropriately.
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.SH ERRORS
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.TP 10
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.B EBADF
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The argument
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.I sockfd
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is not a valid descriptor.
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.TP
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.B EFAULT
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The address pointed to by
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.I optval
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is not in a valid part of the process address space.
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For
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.BR getsockopt (),
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this error may also be returned if
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.I optlen
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is not in a valid part of the process address space.
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.TP
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.B EINVAL
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.I optlen
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invalid in
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.BR setsockopt ().
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In some cases this error can also occur for an invalid value in
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.IR optval
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(e.g., for the
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.B IP_ADD_MEMBERSHIP
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option described in
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.BR ip (7)).
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.TP
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.B ENOPROTOOPT
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The option is unknown at the level indicated.
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.TP
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.B ENOTSOCK
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The argument
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.I sockfd
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is a file, not a socket.
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.SH "CONFORMING TO"
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SVr4, 4.4BSD (these system calls first appeared in 4.2BSD),
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POSIX.1-2001.
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.\" SVr4 documents additional ENOMEM and ENOSR error codes, but does
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.\" not document the
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.\" .BR SO_SNDLOWAT ", " SO_RCVLOWAT ", " SO_SNDTIMEO ", " SO_RCVTIMEO
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.\" options
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.SH NOTES
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POSIX.1-2001 does not require the inclusion of
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.IR <sys/types.h> ,
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and this header file is not required on Linux.
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However, some historical (BSD) implementations required this header
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file, and portable applications are probably wise to include it.
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The
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.I optlen
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argument of
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.BR getsockopt ()
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and
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.BR setsockopt ()
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is in reality an
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.I "int [*]"
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(and this is what 4.x BSD and libc4 and libc5 have).
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Some POSIX confusion resulted in the present
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.IR socklen_t ,
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also used by glibc.
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See also
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.BR accept (2).
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.SH BUGS
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Several of the socket options should be handled at lower levels of the
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system.
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.SH "SEE ALSO"
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.BR ioctl (2),
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.BR socket (2),
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.BR getprotoent (3),
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.BR protocols (5),
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.BR socket (7),
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.BR tcp (7),
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.BR unix (7)
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