uschar **errmsg where to put an error message if there is a problem
The yield of xxx_open() is a void * value representing the open file or
-database. For real files is is normally the FILE or DBM value. For other
+database. For real files it is normally the FILE or DBM value. For other
kinds of lookup, if there is no natural value to use, (-1) is recommended.
The value should not be NULL (or 0) as that is taken to indicate failure of
the xxx_open() function. For single-key lookups, the handle is cached along
If set to a nonzero number of seconds, the cached value
becomes unusable after this time. Currently the dnsdb
lookup uses this to support the TTL value.
+ uschar *opts options, a comma-separated list of tagged values for
+ modifying the search operation
Even though the key is zero-terminated, the length is passed because in the
common case it has been computed already and is often needed.