Host and user specifications are given as regular expressions that are matched against the string ``user@host'' where user is the userID string passed to faxd.recv(1M) and host is either the official host name or the DARPA Internet address, specified in ``dot notation''. If a regular expression has a leading ``!'', then it is interpreted as a class of hosts and users to which access is to be disallowed. That is, if the pattern matches the client information, then access is denied.
Each regular expression pattern must appear on a line by itself. Trailing white space is ignored. Comments are introduced with the ``#'' character and extend to the end of the line. For backwards compatibility, host name patterns without a user specification are interpreted as ``.*@host''; i.e. any user on that host may submit a jobs for transmission.
The following is a sample hosts file.
127.0.0.1 # anyone coming through local host sam@flake.*sgi.com # Sam on his work machine sam@oxford.*Berkeley.* # Sam on his machine at home .*@.*.\.esd\..* # anyone in the esd domain !tom@.* # Tom Davis is denied access, .*\.sgi.com # but anyone else at sgi is ok