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 that 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, 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
     residing at the well-known Internet port inport.

     If the call succeeds, a socket of type SOCK_STREAM is
     returned 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
     descriptor for it will be placed in *fd2p.  The control
     process will return the stderr (descriptor 2 of the
     remote(1M) command) 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 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
     privileged address bound to it.  This socket is suitable for



January 1992                                                    1

rcmd(3N)                                                 rcmd(3N)



     use by rcmd and several other routines.  Privileged
     addresses 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.

LIMITATIONS
     There is no way to specify options to the socket call that
     rcmd makes.

SEE ALSO
     rexec(3N)

     remsh(1N), rlogin(1N) in A/UX Command Reference remshd(1M),
     rexecd(1M), rlogind(1M) in A/UX System Administrator's
     Reference





























2                                                    January 1992