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AnyDBM_File(3pm)		 Perl Programmers Reference Guide		 AnyDBM_File(3pm)

       AnyDBM_File - provide framework for multiple DBMs

       NDBM_File, DB_File, GDBM_File, SDBM_File, ODBM_File - various DBM implementations

	   use AnyDBM_File;

       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 (See DB_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 POSIX; 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.

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

perl v5.8.0				    2002-06-01				 AnyDBM_File(3pm)
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