AnyDBM_File

CONTENTS

• NAME
• SYNOPSIS
• DESCRIPTION
  • DBM Comparisons
• SEE ALSO

NAME

AnyDBM_File - provide framework for multiple DBMs

NDBM_File, DB_File, GDBM_File, SDBM_File, ODBM_File - various 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 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:

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 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;

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 DB_File. Requires symbolic links.

[3]

By default, but can be redefined.

SEE ALSO

dbm(3), ndbm(3), DB_File(3), perldbmfilter