AnyDBM_File(3) Perl Programmers Reference Guide AnyDBM_File(3)NAMEAnyDBM_File - provide framework for multiple DBMs
NDBM_File, DB_File, GDBM_File, SDBM_File, ODBM_File - var
ious DBM implementations
SYNOPSIS
use AnyDBM_File;
DESCRIPTION
This module is a "pure virtual base class"--it has nothing
of its own. It's just there to inherit from one of the
various DBM packages. It prefers ndbm for compatibility
reasons with Perl 4, then Berkeley DB (See the DB_File
manpage), GDBM, SDBM (which is always there--it comes with
Perl), and finally ODBM. This way old programs that used
to use NDBM via dbmopen() can still do so, but new ones
can reorder @ISA:
BEGIN { @AnyDBM_File::ISA = qw(DB_File GDBM_File NDBM_File) }
use AnyDBM_File;
Having multiple DBM implementations makes it trivial to
copy database formats:
use POSIX; use NDBM_File; use DB_File;
tie %newhash, 'DB_File', $new_filename, O_CREAT|O_RDWR;
tie %oldhash, 'NDBM_File', $old_filename, 1, 0;
%newhash = %oldhash;
DBM Comparisons
Here's a partial table of features the different packages
offer:
odbm ndbm sdbm gdbm bsd-db
---- ---- ---- ---- ------
Linkage comes w/ perl yes yes yes yes yes
Src comes w/ perl no no yes no no
Comes w/ many unix os yes yes[0] no no no
Builds ok on !unix ? ? yes yes ?
Code Size ? ? small big big
Database Size ? ? small big? ok[1]
Speed ? ? slow ok fast
FTPable no no yes yes yes
Easy to build N/A N/A yes yes ok[2]
Size limits 1k 4k 1k[3] none none
Byte-order independent no no no no yes
Licensing restrictions ? ? no yes no
[0] on mixed universe machines, may be in the bsd compat
library, which is often shunned.
[1] Can be trimmed if you compile for one access method.
[2] See the DB_File manpage. Requires symbolic links.
[3] By default, but can be redefined.
SEE ALSOdbm(3), ndbm(3), DB_File(3), the perldbmfilter manpage
2001-02-22 perl v5.6.1 AnyDBM_File(3)
