perl 大型DBM文件排序

[perl]代码库

#-----------------------------
use DB_File;

# specify the Perl sub to do key comparison using the
# exported $DB_BTREE hash reference
$DB_BTREE-> {'compare'} = sub
{
	my ( $key1, $key2 ) = @_ ;
	return "\L$key1" cmp "\L$key2";
};

tie ( %hash, "DB_File", $filename, O_RDWR|O_CREAT, 0666, $DB_BTREE )
or die "can't tie $filename: $!";
#-----------------------------
# download the following standalone program
#!/usr/bin/perl
# sortdemo - show auto dbm sorting
use strict;
use DB_File;

$DB_BTREE-> {'compare'} = sub
{
	my ( $key1, $key2 ) = @_ ;
	"\L$key1"
	cmp "\L$key2" ;
};

my %hash;
my $filename = '/tmp/sorthash.db';
tie ( %hash, "DB_File", $filename, O_RDWR|O_CREAT, 0666, $DB_BTREE )
or die "can't tie $filename: $!";

my $i = 0;
for my $word ( qw ( Can't you go camp down by Gibraltar)) {
                    $hash{$word} = ++$i;
                    }

                    while (my($word, $number) = each %hash) {
                    printf "%-12s %d\n", $word, $number;
                    }

#-----------------------------
#by           6
#
#camp         4
#
#Can't        1
#
#down         5
#
#Gibraltar    7
#
#go           3
#
#you          2
#-----------------------------
                    tie ( %hash, "DB_File", undef, O_RDWR|O_CREAT, 0666, $DB_BTREE )
                    or die "can't tie: $!";
#-----------------------------