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<body>
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<pre>
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NAME
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getsockopt, setsockopt - get and set options on sockets
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SYNOPSIS
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#include <network.h>
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int getsockopt(int s, int level, int optname, void *opt
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val, socklen_t *optlen);
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int setsockopt(int s, int level, int optname, const void
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*optval, socklen_t optlen);
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DESCRIPTION
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Getsockopt and setsockopt manipulate the options associ
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ated with a socket. Options may exist at multiple proto
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col 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 speci
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fied. To manipulate options at the socket level, level is
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specified as SOL_SOCKET. To manipulate options at any
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other level the protocol number of the appropriate proto
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col controlling the option is supplied. For example, to
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indicate that an option is to be interpreted by the TCP
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protocol, level should be set to the protocol number of
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TCP; see getprotoent(3).
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The parameters optval and optlen are used to access option
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values for setsockopt. For getsockopt they identify a
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buffer in which the value for the requested option(s) are
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to be returned. For getsockopt, optlen is a value-result
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parameter, initially containing the size of the buffer
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pointed to by optval, and modified on return to indicate
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the actual size of the value returned. If no option value
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is to be supplied or returned, optval may be NULL.
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Optname and any specified options are passed uninterpreted
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to the appropriate protocol module for interpretation.
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The include file <network.h> contains definitions for
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socket level options, described below. Options at other
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protocol levels vary in format and name; consult the
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appropriate entries in section 4 of the manual.
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Most socket-level options utilize an int parameter for
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optval. For setsockopt, the parameter should be non-zero
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to enable a boolean option, or zero if the option is to be
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disabled.
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For a description of the available socket options see
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socket(7) and the appropriate protocol man pages.
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RETURN VALUE
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On success, zero is returned. On error, -1 is returned,
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and errno is set appropriately.
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ERRORS
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EBADF The argument s is not a valid descriptor.
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ENOTSOCK
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The argument s is a file, not a socket.
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ENOPROTOOPT
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The option is unknown at the level indicated.
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</pre>
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</body>
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</html>
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