AnyDBM_File − provide framework for multiple DBMs
NDBM_File, DB_File, GDBM_File, SDBM_File, ODBM_File − various DBM implementations
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 DB_File), 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:
@AnyDBM_File::ISA = qw(DB_File GDBM_File NDBM_File) }
Having multiple DBM implementations makes it trivial to copy database formats:
use Fcntl; 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;
Here’s a partial table of features the different packages offer:
odbm ndbm sdbm
−−−− −−−− −−−− −−−− −−−−−−
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 no no no
Builds ok on !unix ? ? yes yes ?
Code Size ? ? small big big
Database Size ? ? small big? ok
Speed ? ? slow ok fast
FTPable no no yes yes yes
Easy to build N/A N/A yes yes ok
Size limits 1k 4k 1k none none
Byte−order independent no no no no yes
Licensing restrictions ? ? no yes no
on mixed universe machines, may be in the bsd compat library, which is often shunned.
Can be trimmed if you compile for one access method.
See DB_File. Requires symbolic links.
By default, but can be redefined.
dbm(3), ndbm(3), DB_File(3), perldbmfilter