rcmd(3N)                                                 rcmd(3N)



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

     SYNOPSIS
          rem = rcmd(ahost, inport, locuser, remuser, cmd, fd2p);
          char**ahost;
          ushort 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
          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 remshd(1M) server (among others).

          rcmd looks up the host *ahost using gethostent(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 call succeeds, a socket of type SOCKSTREAM 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 forwarded 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 remshd(1M).

          The rresvport routine is used to obtain a socket with a



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     rcmd(3N)                                                 rcmd(3N)



          privileged address bound to it.  This socket is suitable for
          use by rcmd and several other routines.  Privileged
          addresses consist of a port 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
          gethostent(3N) routine, two user names and a flag indicating
          if the local user's name is the super-user.  It then checks
          the files /etc/hosts.equiv and, possibly, .rhosts in the
          current working directory (normally the local user's home
          directory) to see if the request for service is allowed.  A
          1 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 0.
          If the superuser flag is 1, the checking of the
          ``host.equiv'' file is bypassed.

     SEE ALSO
          rlogin(1N), remsh(1N), rexec(3N), rexecd(1M), rlogind(1M),
          remshd(1M).

     BUGS
          There is no way to specify options to the socket call which
          rcmd makes.






























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