The file types are:

      DB_HASH
            This database type allows arbitrary key/data pairs to
            be stored in data files. This is equivalent to the
            functionality provided by other hashing packages like
            DBM, NDBM, ODBM, GDBM, and SDBM. Remember though, the
            files created using DB_HASH are not compatible with
            any of the other packages mentioned.

            A default hashing algorithm, which will be adequate
            for most applications, is built into Berkeley DB. If
            you do need to use your own hashing algorithm it is
            possible to write your own in Perl and have DB_File use it instead.
       DB_BTREE
            The btree format allows arbitrary key/data pairs to
            be stored in a sorted, balanced binary tree.

            As with the DB_HASH format, it is possible to provided
            a user defined Perl routine to perform the comparison
            of keys. By default, though, the keys are stored in
            lexical order.

       DB_RECNO
            DB_RECNO allows both fixed-length and variable-length
            flat text files to be manipulated using the same
            key/value pair interface as in DB_HASH and DB_BTREE.
            In this case the key will consist of a record (line)
            number.

Example using Hashed

               tie %h,  "DB_File", "hashed", O_RDWR|O_CREAT, 0640, $DB_HASH ;

               # Add a key/value pair to the file
               $h{"apple"} = "orange" ;

               # Check for existence of a key
               print "Exists\n" if $h{"banana"} ;

               # Delete
               delete $h{"apple"} ;

               untie %h ;

 

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Example Using Tree

               use DB_File ;
               use Fcntl ;

               sub Compare
               {
                   my ($key1, $key2) = @_ ;

                   "\L$key1" cmp "\L$key2" ;
               }

               $DB_BTREE->{compare} = 'Compare' ;

               tie %h,  'DB_File', "tree", O_RDWR|O_CREAT, 0640, $DB_BTREE ;

               # Add a key/value pair to the file
               $h{'Wall'} = 'Larry' ;
               $h{'Smith'} = 'John' ;
               $h{'mouse'} = 'mickey' ;
               $h{'duck'}   = 'donald' ;

               # Delete
               delete $h{"duck"} ;

               # Cycle through the keys printing them in order.
               # Note it is not necessary to sort the keys as
               # the btree will have kept them in order automatically.
               foreach (keys %h)
                 { print "$_\n" }

               untie %h ;




Example Using DB_RECNO

               use DB_File ;
               use Fcntl ;

               $DB_RECNO->{psize} = 3000 ;

               tie @h,  DB_File, "text", O_RDWR|O_CREAT, 0640, $DB_RECNO ;

               # Add a key/value pair to the file
               $h[0] = "orange" ;

               # Check for existence of a key
               print "Exists\n" if $h[1] ;

               untie @h ;