3.2 on page 887 Append tag on successful match.
-D ?§23.3.3 on page 887 Don??™t use this database map if DeliveryMode=defer.
-S ?§23.3.12 on page 890 Space replacement character
-s Synonym for -S
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23.7 Alphabetized Database-Map Types | 901
23.7.2 btree
The db(3) form of database V8.1 and later
The term btree stands for ???balanced tree.??? It is a grow-only form of database. Lookups and
insertions are fast, but deletions do not shrink the size of the database file.* A good description
of this form of database can be found in The Art of Computer Programming, Vol. 3:
Sorting and Searching, by D.E. Knuth. The btree type is available only if sendmail was
compiled with NEWDB defined and the Berkeley or Sleepycat db library linked (?§3.1.1 on
page 104). In most cases, the hash type (?§23.7.7 on page 908) will perform slightly better.
Quite a few database switches are available with this database-map type. They are listed in
Table 23-7.
One use for this btree type might be to look up users for whom permission to send offsite
email is denied. The data source file might look like the following, and might live in the file
/etc/mail/badusers.db (after makemap was run to create it):
bob bob
ted ted
alice alice
A simple configuration file to test this database can then be created like this:
V10
Kbaduser btree -a.
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