Example 19-1. btree2hash.pl

#!/usr/bin/perl -w

#
# This script takes as its parameters a list of Berkeley DB
# file(s) which are stored with the DB_BTREE algorithm.  It
# will back them up using the .bak extension and create
# instead DBMs with the same records but stored using the
# DB_HASH algorithm.
#
# Usage: btree2hash.pl filename(s)

use strict;
use DB_File;
use Fcntl;

# @ARGV checks
die "Usage: btree2hash.pl filename(s))\n" unless @ARGV;

for my $filename (@ARGV) {
    die "Can't find $filename: $!"
        unless -e $filename and -r _;

    # First back up the file
    rename "$filename", "$filename.btree" 
        or die "can't rename $filename with $filename.btree: $!";

    # tie both DBs (db_hash is a fresh one!)
    tie my %btree , 'DB_File',"$filename.btree", O_RDWR|O_CREAT,
        0660, $DB_BTREE or die "Can't tie $filename.btree: $!";
    tie my %hash ,  'DB_File',"$filename" , O_RDWR|O_CREAT,
        0660, $DB_HASH  or die "Can't tie $filename: $!";

    # copy DB
    %hash = %btree;

    # untie
    untie %btree;
    untie %hash;
}