arguments recognized:

"no_hosts_equiv"
"no_rhosts"
"debug"
"nowarn"
"suppress"
"promiscuous"

.rhosts/hosts.equiv format:

There are positive entries, when one is matched authentication
succeeds and terminates.  There are negative entries, when one is
matched authentication fails and terminates.  Thus order is
significant.

Entry          hosts.equiv                     .rhosts
<host>         All users on <host> are ok      Same username from <host> is ok
<host> <user>  <user> from <host> is ok        ditto
-<host>                No users from <host> are ok     ditto
<host> -<user> <user> from <host> is not ok    ditto

<host> can be ip (IPv4) numbers.

Netgroups may be used in either host or user fields, and then applies
to all hosts, or users, in the netgroup.  The syntax is

  +@<ng>

The entries

  <host> +@<ng>
  +@<ng> +@<ng>
  +@<ng> <user>

means exactly what you think it does.  Negative entries are of the
form

  -@<ng>

When the "promiscuous" option is given the special character + may be
used as a wildcard in any field.

  +                    Allow anyone from any host to connect. DANGEROUS.
  + +                  Ditto.
  + <user>             Allow the user to connect from anywhere. DANGEROUS.
  <host> +             Allow any user from the host. Dangerous.
  
These, perhaps more useful, forms of the + form is also disallowed
unless "promiscuous" is specified:

  + -<user>            Disallow the user from any host
  + -@<ng>             Disallow all members of the netgroup from any host

When "promiscuous" is not specified a '+' is handled as a negative
match.