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 (SeeDB_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]

SeeDB_File. Requires symbolic links.

#[3]

By default, but can be redefined.

#SEE ALSO

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

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