rcmd(3N)                                                    rcmd(3N)


       NAME
             rcmd, rresvport, ruserok - routines for returning a stream to
             a remote command

       SYNOPSIS
             cc [options] file -lsocket -lnsl
             #include <netdb.h>
             int rcmd(char **ahost, unsigned short inport, char *luser, char *ruser,
                   char *cmd, int *fd2p);
             int rresvport(int *port);
             int ruserok(char *rhost, int super-user, char *ruser, char *luser);

       DESCRIPTION
             rcmd is a routine used by a privileged user to execute a
             command on a remote machine using an authentication scheme
             based on reserved port numbers.

             rresvport is a routine which returns a descriptor to a socket
             with an address in the privileged port space.

             ruserok is a routine used by servers to authenticate clients
             requesting service with rcmd.

             All three functions are present in the same file and are used
             by the rshd server (among others).

             rcmd looks up the host *ahost using gethostbyname [see
             gethostent(3N)]. If the host exists, *ahost is set to the
             standard name of the host and a connection is established to a
             server residing at the well-known Internet port inport.

             If the connection succeeds, a socket in the Internet domain of
             type SOCK_STREAM is returned to the caller, and given to the
             remote command as its standard input (file descriptor 0) and
             standard output (file descriptor 1).  If fd2p is non-zero,
             then an auxiliary channel to a control process will be set up,
             and a descriptor for it will be placed in *fd2p.  The control
             process will return diagnostic output from the command (file
             descriptor 2) on this channel, and will also accept bytes on
             this channel as signal numbers, to be forwarded to the process
             group of the command.  If fd2p is 0, then the standard error
             (file descriptor 2) of the remote command will be made the
             same as its standard output and no provision is made for
             sending arbitrary signals to the remote process, although you
             may be able to get its attention by using out-of-band data.



                           Copyright 1994 Novell, Inc.               Page 1

      rcmd(3N)                                                    rcmd(3N)


            The protocol is described in detail in rshd [see rshd(1M)].

            The rresvport routine is used to obtain a socket with a
            privileged address bound to it.  This socket is suitable for
            use by rcmd and several other routines.  Privileged Internet
            ports are those in the range 0 to 1023.  Only a user with
            appropriate privileges is allowed to bind an address of this
            sort to a socket.

            ruserok takes a remote host's name, two user names and a flag
            indicating whether the local user's name is that of the
            privileged user.  If the privileged user flag is 0, the
            routine then checks the file /etc/hosts.equiv.  If this check
            fails, then the routine checks in the local user's home
            directory to see if the request for service is allowed.  If
            .rhosts is writeable by group or other, then access is denied.

         Files
            /etc/hosts.equiv
            /usr/lib/locale/locale/LC_MESSAGES/uxnsl

         Return Values
            rcmd returns a valid socket descriptor on success.  It returns
            -1 on error and prints a diagnostic message on the standard
            error.

            rresvport returns a valid, bound socket descriptor on success.
            It returns -1 on error with the global value errno set
            according to the reason for failure.  The error code EAGAIN is
            overloaded to mean:
                  All network ports in use.
            ruserok returns a 0 if the machine name is listed in the
            /etc/hosts.equiv file or if the host and remote user name are
            found in the

      REFERENCES
            gethostent(3N), intro(2), rexec(3N), rexecd(1M), rlogin(1),
            rlogind(1M), rsh(1), rshd(1M)










                          Copyright 1994 Novell, Inc.               Page 2