rcmd(3x)
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rcmd, rresvport, ruserok Subroutine
routines for returning a stream to a remote command
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SYNTAX
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 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 authenticate clients
requesting service with rcmd.
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 descriptor 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 DG/UX system 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 rresvport routine is used to obtain a socket with a
DG/UX 4.00 Page 1
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rcmd(3x)
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
gethostent(3N) routine, two user names and a flag indicating 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(3X), rexecd(8C), rlogind(8C),
BUGS
There is no way to specify options to the socket call which rcmd
makes.
DG/UX 4.00 Page 2
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