getsockopt(2N)                                     getsockopt(2N)



NAME
     getsockopt, setsockopt - get and set options on sockets

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

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

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

DESCRIPTION
     getsockopt and setsockopt manipulate options associated with
     a socket.  Upon successful completion, both getsockopt and
     setsockopt return 0. A return value of -1 indicates failure.

     Options can exist at multiple protocol levels; they are
     always present at the uppermost ``socket'' level.  When
     manipulating socket options, you must specify the level at
     which the option resides and the name of the option.  To
     manipulate options at the ``socket'' level, specify level as
     SOL_SOCKET.  To manipulate options at any other level,
     supply the protocol number of the appropriate protocol
     controlling the option.  For example, to indicate that an
     option is to be interpreted by the Transmission Control
     Protocol (TCP), set level 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 option(s) is 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 can 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 Section 5 of this manual.
     (Appropriate entries are marked (5P).)





January 1992                                                    1

getsockopt(2N)                                     getsockopt(2N)



STATUS MESSAGES AND VALUES
     When a value of -1 is returned, errno contains one of these
     values:

     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.

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




































2                                                    January 1992