getsockopt(2)              DG/UX 4.30               getsockopt(2)



     NAME
          getsockopt - Get options on a socket.

     SYNOPSIS
          #include <sys/socket.h>

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

     PARAMETERS
          s              File descriptor of socket to get options
                         from.


          level          Level in socket that the options apply to.


          optname        Name of option to return. Options are defined
                         in <sys/socket.h>.


          optval         Buffer to receive options.


          optlen         On input contains the number of bytes
                         available for the options; updated to
                         indicate the number of bytes returned.

     DESCRIPTION
          Getsockopt retrieves options associated with a socket.
          Options may exist at multiple protocol levels; they are
          always present at the uppermost socket level.

          When getting socket options, the caller must specify the
          level at which the option resides and the name of the
          option.  To retrieve options at the socket level, <level> is
          specified as SOL_SOCKET.  To get options at any other level,
          the protocol number of the appropriate protocol controlling
          the option is supplied.  Consult domain specific
          documentation for more information related to a specific
          protocol.

          The parameters <optval> and <optlen> identify a buffer in
          which the value for the requested option(s) are to be
          returned.  <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 returned,



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     getsockopt(2)              DG/UX 4.30               getsockopt(2)



          <optval> may be supplied as 0.  If the buffer isn't large
          enough for the options, they will be truncated.

          <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.  Options at other protocol levels
          vary in format and name; consult the related documentation
          for the domain of the socket.

     ACCESS CONTROL
          SOL_SOCKET has no access restrictions.  (See domain-specific
          documentation for any domain restrictions.)

     RETURN VALUE
          0              Completed successfully.


          -1             An error occurred.  Errno is set to indicate
                         the error.

     EXCEPTIONS
          Errno may be set to one of the following error codes:


          EBADF          The argument <s> is not an active valid
                         descriptor.


          ENOTSOCK       The argument <s> is not a file of type
                         S_IFSOCK (socket special).


          ENOPROTOOPT    The option is unknown.


          EFAULT         The <optval> is not in a valid part of the
                         process address space, or <optlen> < 0.


          ENOBUFS        No internal buffers available.

     SEE ALSO
          The related manual sections:  inet(3N), inet(6F), tcp(6p),
          udp(6p), unix_ipc(6F), setsockopt(2), socket(2).










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