rcmd(3N)                                                 rcmd(3N)



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

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

          int rresvport(port)
          int *port;

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

     DESCRIPTION
          rcmd is a routine used by the superuser 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 authen-
          ticate clients requesting service with rcmd.  All three
          functions are present in the same file and are used by the
          remshd(1M) server, as well as others.

          rcmd looks up the host *ahost, 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 resid-
          ing at the well-known Internet port inport.

          If the call succeeds, a socket of type SOCK_STREAM is re-
          turned to the caller, and given to the remote command as
          stdin and stdout.  If fd2p is nonzero, then an auxiliary
          channel to a control process will be set up, and a descrip-
          tor for it will be placed in *fd2p.  The control process
          will return the stderr (descriptor 2 of the remote(1M) com-
          mand) on this channel and will accept bytes on this channel
          as A/UX signal numbers to be forwarded to the process group
          of the command.  If fd2p is 0, then the stderr (descriptor 2
          of the remote(1M) command) will be made the same as stdout;
          no provision will be made for sending arbitrary signals to
          the remote process, although you may be able to get its at-
          tention 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
          privileged address bound to it.  This socket is suitable for



     April, 1990                                                     1

     rcmd(3N)                                                 rcmd(3N)



          use by rcmd and several other routines.  Privileged ad-
          dresses consist of a port in the range 0 to 1023.  Only the
          superuser 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 if the local user's name is the superuser.
          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 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 checking of the host.equiv file
          is bypassed.

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

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
































     2                                                     April, 1990