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The
function is used by the super-user 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 server (among others). The function looks up the host using
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 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 super-user 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 super-user. Then, if the user
is the super-user, 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 super-user,
or is writeable 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 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.
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.’’
These
functions appeared in
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