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=head1 NAME
AnyDBM_File - provide framework for multiple DBMs
NDBM_File, ODBM_File, SDBM_File, GDBM_File - various DBM implementations
=head1 SYNOPSIS
use AnyDBM_File;
=head1 DESCRIPTION
This module is a "pure virtual base class"--it has nothing of us 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
L<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);
This 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;
=head2 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
=over 4
=item [0]
on mixed universe machines, may be in the bsd compat library,
which is often shunned.
=item [1]
Can be trimmed if you compile for one access method.
=item [2]
See L<DB_File>.
Requires symbolic links.
=item [3]
By default, but can be redefined.
=back
=head1 SEE ALSO
dbm(3), ndbm(3), DB_File(3)
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