DBM Files and the BerkeleyDatabase Manager
DBM files are a storage management layer that allows programmers to store information in files as pairs of strings, a key, and a value. DBM files are binary files and the key and value strings can also hold binary data.
There are several forms of DBM files, each with its own strengths and
weaknesses. Perl supports the
ndbm
,
db
,
gdbm
,
sdbm
, and
odbm
managers via the
NDBM_File
,
DB_File
,
GDBM_File
,
SDBM_File
, and
ODBM_File
extensions. There’s also an
AnyDBM_File
module that will simply use the best
available DBM. The documentation for the
AnyDBM_File
module includes a useful table
comparing the different DBMs.
These extensions all associate a DBM file on disk with a Perl hash variable (or associative array ) in memory.[13] The simple look like a hash programming interface lets programmers store data in operating system files without having to consider how it’s done. It just works.
Programmers store and fetch values into and out of the hash, and the underlying DBM storage management layer will look after getting them on and off the disk.
In this section, we shall discuss the most popular and sophisticated
of these storage managers, the Berkeley Database Manager, also known
as the Berkeley DB. This software is accessed from Perl via the
DB_File
and Berkeley DB extensions. On Windows
systems, it can be installed via the Perl package manager,
ppm. On Unix systems, it is built by default
when Perl is built only if the Berkeley DB library ...
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