rcmd(3N)                      4 BSD                      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 com-
     mand 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 rshd(1M) server (among others).

     rcmd looks up the host *ahost using gethostbyname(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 SOCK_STREAM 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 descrip-
     tor 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 rshd(1M).





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rcmd(3N)                      4 BSD                      rcmd(3N)



     The rresvport routine is used to obtain a socket with a
     privileged address bound to it.  This socket is suitable for
     use by rcmd and sevral 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
     gethostbyname(3N) routine, two user names and a flag indi-
     cating 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(1C), rsh(1C), rexec(3N), rexecd(1M), rlogind(1M),
     rshd(1M)

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






























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