NAME
SYNOPSIS
DESCRIPTION
The
function
is used by the superuser to execute a command on
a remote machine using an authentication scheme based
on reserved port numbers.
The
function
returns a descriptor to a socket
with an address in the privileged port space.
The
and
functions are used by servers
to authenticate clients requesting service with
All four functions are present in the same file and are used
by the
rshd(8)
server (among others).
The
function
looks up the host
using
gethostbyname(3)
returning -1 if the host does not exist.
Otherwise
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
is returned to the caller, and given to the remote
command as
and
If
is non-zero, then an auxiliary channel to a control
process will be set up, and a descriptor for it will be placed
in
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
signal numbers, to be
forwarded to the process group of the command.
If
is 0, then the
(unit 2 of the remote
command) will be made the same as the
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(8)
The
function is used to obtain a socket with a privileged
address bound to it.
This socket is suitable for use by
and several other functions.
Privileged Internet ports are those in the range 0 to 1023.
Only the superuser is allowed to bind an address of this sort to a socket.
The
and
functions take a remote host's IP address or name, respectively,
two user names and a flag indicating whether the local user's
name is that of the superuser.
Then, if the user is
the superuser, it checks the
file.
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 does not exist, is not a regular file, is owned by anyone
other than the user or the superuser, or is writable by anyone other
than the owner, the check automatically fails.
Zero is returned if the machine name is listed in the
file, or the host and remote user name are found in the
file; otherwise
and
return -1.
If the local domain (as obtained from
gethostname(2)
is the same as the remote domain, only the machine name need be specified.
If the IP address of the remote host is known,
should be used in preference to
as it does not require trusting the DNS server for the remote host's domain.
RETURN VALUE
The
function
returns a valid socket descriptor on success.
It returns -1 on error and prints a diagnostic message on the standard error.
The
function
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
is overloaded to mean ``All network ports in use.''
CONFORMING TO
Not in POSIX.1-2001.
Present on the BSDs, Solaris, and many other systems.
These
functions appeared in
x 4.2 .
SEE ALSO
ČLÁNKY DO MAILU