AnyDBM_File (3)

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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 packages. It prefers ndbm for compatibility reasons with Perl 4, then Berkeley (See DB_File), (which is always there---it comes with Perl), and finally This way old programs that used to use 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

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