getsockopt(2N)                                     getsockopt(2N)



     NAME
          getsockopt, setsockopt - get and set options on sockets

     SYNOPSIS
          #include <sys/types.h>
          #include <sys/socket.h>

          getsockopt(s, level, optname, optval, optlen)
          int s, level, optname;
          char *optval;
          int *optlen;

          setsockopt(s, level, optname, optval, optlen)
          int s, level, optname;
          char *optval;
          int *optlen;

          cc ... -lnet

     DESCRIPTION
          getsockopt and setsockopt manipulate options associated with
          a socket.  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 ``socket'' level, level is
          specified as SOLSOCKET.  To manipulate options at any other
          level the protocol number of the appropriate protcol
          controlling the option is supplied.  For example, to
          indicate an option is to be interpreted by the TCP protocol,
          level should be set to the protocol number of TCP; see
          getprotoent(3N).

          The parameters optval and optlen are used to access option
          values for setsockopt.  For getsockopt they identify a
          buffer in which the value of the requested options(s) are to
          be returned.  For getsockopt, optlen is a value-result
          parameter, initially containing the size of the buffer
          pointed to by optval , and modified on return to indicate
          the actual size of the value returned.  If no option value
          is to be supplied or returned, optval may be supplied as 0.

          optname and any specified options are passed uninterpreted
          to the appropriate protocol module for interpretation.  The
          include file <sys/socket.h> contains definitions for
          ``socket'' level options; see socket(2N).  Options at other
          protocol levels vary in format and name, consult the
          appropriate entries in (5P).

     RETURN VALUE
          A 0 is returned if the call succeeds, -1 if it fails.



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     getsockopt(2N)                                     getsockopt(2N)



     ERRORS
          The call succeeds unless:


          [EBADF]        The argument s is not a valid descriptor.

          [ENOTSOCK]     The argument s is a file, not a socket.

          [ENOPROTOOPT]  The option is unknown.

          [EFAULT]       The options are not in a valid part of the
                         process address space.

     LINKING
          This library is accessed by specifying -lnet as the last
          argument to the compile line, e.g.:

            cc -o prog prog.c -lnet

     SEE ALSO
          socket(2N), getprotoent(3N).


































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