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;
          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(3N). 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.


          ruserok uses the remote host's name returned by the



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     RCMD(3N)                                                 RCMD(3N)



          raddr(3N) gethostent(3N) routine, 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(1C), rsh(1C), rlogind(1M), rshd(1M)

     ORIGIN
          4.3 BSD









































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