# 2.11BSD#431 - /usr/man/cat3/rcmd.0

    RCMD(3)             UNIX Programmer's Manual		  RCMD(3)

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

    SYNOPSIS
         rem = rcmd(ahost, inport, locuser, remuser, cmd, fd2p);
         char **ahost;
         int inport;
         char *locuser, *remuser, *cmd;
         int *fd2p;

         s = rresvport(port);
         int *port;

         ruserok(rhost, superuser, ruser, luser);
         char *rhost;
         int superuser;
         char *ruser, *luser;

    DESCRIPTION
         Rcmd is a routine used by the super-user to execute a com-
         mand 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(8C) server (among others).

         Rcmd looks up the host *ahost using gethostbyname(3N),
         returning -1 if the host does not exist.  Otherwise *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 stdin and stdout.  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 (unit 2) on this channel, and will also accept bytes
         on this channel as being UNIX signal numbers, to be for-
         warded to the process group of the command.  If fd2p is 0,
         then the stderr (unit 2 of the remote command) will be made
         the same as the stdout 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.

         The protocol is described in detail in rshd(8C).

    Printed 11/26/99	  May 14, 1986				1

    RCMD(3)             UNIX Programmer's Manual		  RCMD(3)

         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 the super-user
         is allowed to bind an address of this sort to a socket.

         Ruserok takes a remote host's name, as returned by a
         gethostbyaddr(3N) routine, two user names and a flag indi-
         cating whether the local user's name is that of the super-
         user.  It then checks the files /etc/hosts.equiv and, possi-
         bly, .rhosts in the current working directory (normally the
         local user's home directory) to see if the request for ser-
         vice is allowed.  A 0 is returned if the machine name is
         listed in the ``hosts.equiv'' file, or the host and remote
         user name are found in the ``.rhosts'' file; otherwise
         ruserok returns -1.  If the superuser flag is 1, the check-
         ing of the ``host.equiv'' file is bypassed.  If the local
         domain (as obtained from gethostname(2)) is the same as the
         remote domain, only the machine name need be specified.

    SEE ALSO
         rlogin(1C), rsh(1C), intro(2), rexec(3), rexecd(8C),
         rlogind(8C), rshd(8C)

    DIAGNOSTICS
         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 suc-
         cess.  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.''

    Printed 11/26/99	  May 14, 1986				2

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