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.\" ========================================================================
.\"
.IX Title "AnyDBM_File 3"
.TH AnyDBM_File 3 "2019-10-24" "perl v5.30.2" "Perl Programmers Reference Guide"
.\" For nroff, turn off justification. Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
AnyDBM_File \- provide framework for multiple DBMs
.PP
NDBM_File, DB_File, GDBM_File, SDBM_File, ODBM_File \- various DBM implementations
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& use AnyDBM_File;
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This module is a \*(L"pure virtual base class\*(R"\-\-it has nothing of its own.
It's just there to inherit from one of the various \s-1DBM\s0 packages. It
prefers ndbm for compatibility reasons with Perl 4, then Berkeley \s-1DB\s0 (See
DB_File), \s-1GDBM, SDBM\s0 (which is always there\*(--it comes with Perl), and
finally \s-1ODBM.\s0 This way old programs that used to use \s-1NDBM\s0 via \fBdbmopen()\fR
can still do so, but new ones can reorder \f(CW@ISA:\fR
.PP
.Vb 2
\& BEGIN { @AnyDBM_File::ISA = qw(DB_File GDBM_File NDBM_File) }
\& use AnyDBM_File;
.Ve
.PP
Having multiple \s-1DBM\s0 implementations makes it trivial to copy database formats:
.PP
.Vb 4
\& use Fcntl; use NDBM_File; use DB_File;
\& tie %newhash, \*(AqDB_File\*(Aq, $new_filename, O_CREAT|O_RDWR;
\& tie %oldhash, \*(AqNDBM_File\*(Aq, $old_filename, 1, 0;
\& %newhash = %oldhash;
.Ve
.SS "\s-1DBM\s0 Comparisons"
.IX Subsection "DBM Comparisons"
Here's a partial table of features the different packages offer:
.PP
.Vb 10
\& 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
.Ve
.IP "[0]" 4
.IX Item "[0]"
on mixed universe machines, may be in the bsd compat library,
which is often shunned.
.IP "[1]" 4
.IX Item "[1]"
Can be trimmed if you compile for one access method.
.IP "[2]" 4
.IX Item "[2]"
See DB_File.
Requires symbolic links.
.IP "[3]" 4
.IX Item "[3]"
By default, but can be redefined.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBdbm\fR\|(3), \fBndbm\fR\|(3), \fBDB_File\fR\|(3), perldbmfilter