[Chapter 8] 8.40 DB

8.40 DB_File

Ties a Perl hash to one of the Berkeley DB database types and lets you use functions provided in the DB API:

[$X =] tie %hash,  "DB_File", $filename [, $flags, $mode, $DB_HASH];
[$X =] tie %hash,  "DB_File", $filename, $flags, $mode, $DB_BTREE;
[$X =] tie @array, "DB_File", $filename, $flags, $mode, $DB_RECNO;

The types are:

$DB_HASH: Stores key/data pairs in data files; equivalent to other hashing packages like DBM, NDBM, ODBM, GDBM, and SDBM.
$DB_BTREE: Stores key/data pairs in a binary tree.
$DB_RECNO: Uses a record (line) number to access fixed-length and variable-length flat text files through the same key/value-pair interface as in $DB_HASH and $DB_BTREE .

After you've tie d a hash to a database:

$db = tie %hash, "DB_File", "filename";

you can access the Berkeley DB API functions:

$db->put($key, $value, R_NOOVERWRITE);  # invoke the DB "put" function

All the functions defined in the dbopen(3) manpage are available except


close

and


dbopen

itself. The constants defined in the dbopen manpage are also available.

Here are the functions available (the comments note only the differences from the equivalent C function):