.\" Copyright (c) 1983 The Regents of the University of California.
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.\" @(#)rcmd.3 6.10 (Berkeley) 6/23/90
.TH RCMD 3 "June 23, 1990"
rcmd, rresvport, ruserok \- routines for returning a stream to a remote command
.B "rem = rcmd(ahost, inport, locuser, remuser, cmd, fd2p);"
.B "char *locuser, *remuser, *cmd;"
.B "ruserok(rhost, superuser, ruser, luser);"
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.
is a routine which returns a descriptor to a socket
with an address in the privileged port space.
is a routine used by servers
to authenticate clients requesting service with
All three functions are present in the same file and are used
returning \-1 if the host does not exist.
is set to the standard name of the host
and a connection is established to a server
residing at the well-known Internet port
If the connection succeeds,
a socket in the Internet domain of type SOCK_STREAM
is returned to the caller, and given to the remote
is non-zero, then an auxiliary channel to a control
process will be set up, and a descriptor for it will be placed
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.
command) will be made the same as the
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
routine is used to obtain a socket with a privileged
address bound to it. This socket is suitable for use
and several other routines. Privileged Internet ports are those
in the range 0 to 1023. Only the super-user
is allowed to bind an address of this sort to a socket.
takes a remote host's name, as returned by the
routine, two user names and a flag indicating whether
the local user's name is that of the super-user. Then,
the super-user, it checks the files
If that lookup is not done, or is unsuccessful, the
in the local user's home directory is checked to see if the request for
service is allowed. If this file is owned by anyone other than the
user or the super-user, or if it is writeable by anyone other than the
owner, the check automatically fails. 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
If the local domain (as obtained from \fIgethostname\fP\|(2))
is the same as the remote domain, only the machine name need be specified.
rlogin(1), rsh(1), intro(2), rexec(3), rexecd(8), rlogind(8), rshd(8)
returns a valid socket descriptor on success.
It returns -1 on error and prints a diagnostic message on the standard error.
returns a valid, bound socket descriptor on success.
It returns -1 on error with the global value
set according to the reason for failure.
The error code EAGAIN is overloaded to mean ``All network ports in use.''
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