RCMD(3N-SVR3)       RISC/os Reference Manual        RCMD(3N-SVR3)



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(options);
     int options;

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

DESCRIPTION
     rcmd executes a command on a remote machine. It uses an
     authentication scheme based on reserved port numbers. Only
     the super user can use this command. rresvport returns a
     descriptor with an address in the privileged port space to a
     socket.  ruserok authenticates clients requesting service
     with rcmd.  All three functions are in the same file.
     rshd(1M) and other servers use these functions.

     rcmd looks up the host *ahost using gethostbyname(3N).  It
     returns -1 if the host does not exist.  Otherwise, *ahost
     becomes the standard name of the host, and a connection is
     established to a server residing at the Internet port
     inport.

     If the call succeeds, a SOCK_STREAM type socket is returned
     to the caller and then given to the remote command as stdin
     and stdout.  This socket has the options specified in
     socket(2).  If fd2p is nonzero, an auxiliary channel to a
     control process is set up and a descriptor for it is placed
     in *fd2p.  The control process returns diagnostic output
     from the command (unit 2) and accepts bytes (as UNIX signal
     numbers) for forwarding to the command's process group on
     this channel. If fd2p is 0, the stderr (unit 2 of the remote
     command) becomes the stdout and arbitrary signals cannot be
     sent to the remote process.  See rshd(1M) for more details.

     rresvport obtains a socket with a privileged address bound
     to it.  rcmd and other routines use this socket.  Privileged
     addresses consist of a port in the range 0 to 1023.  Only
     the super user can bind a privileged address to this socket.






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RCMD(3N-SVR3)       RISC/os Reference Manual        RCMD(3N-SVR3)



     ruserok uses the remote host's name returned by the raddr
     gethostent routine (see gethostbyname(3N), and two user
     names.  Then it checks the files /etc/hosts.equiv  and
     .rhosts in the current working directory (the local user's
     home directory) to see if the service request is allowed.
     It returns a 1 if the hosts.equiv file has the machine name
     and the local and remote user are the same (and the local
     user is not root) or if the .rhosts file has the remote user
     name. Otherwise, ruserok returns a 0.

SEE ALSO
     rlogin(1), rsh(1C) in the User's Reference Manual.
     rlogind(1M), rshd(1M) in the System Administrator's Refer-
     ence Manual.

ORIGIN
     4.3BSD






































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