<html><head><meta name="color-scheme" content="light dark"></head><body><pre style="word-wrap: break-word; white-space: pre-wrap;">package SDBM_File;

use strict;
use warnings;

require Tie::Hash;
require XSLoader;

our @ISA = qw(Tie::Hash);
our $VERSION = "1.14";

our @EXPORT_OK = qw(PAGFEXT DIRFEXT PAIRMAX);
use Exporter "import";

XSLoader::load();

1;

__END__

=head1 NAME

SDBM_File - Tied access to sdbm files

=head1 SYNOPSIS

 use Fcntl;   # For O_RDWR, O_CREAT, etc.
 use SDBM_File;

 tie(%h, 'SDBM_File', 'filename', O_RDWR|O_CREAT, 0666)
   or die "Couldn't tie SDBM file 'filename': $!; aborting";

 # Now read and change the hash
 $h{newkey} = newvalue;
 print $h{oldkey}; 
 ...

 untie %h;

=head1 DESCRIPTION

C&lt;SDBM_File&gt; establishes a connection between a Perl hash variable and
a file in SDBM_File format.  You can manipulate the data in the file
just as if it were in a Perl hash, but when your program exits, the
data will remain in the file, to be used the next time your program
runs.

=head2 Tie

Use C&lt;SDBM_File&gt; with the Perl built-in C&lt;tie&gt; function to establish
the connection between the variable and the file.

    tie %hash, 'SDBM_File', $basename, $modeflags, $perms;

    tie %hash, 'SDBM_File', $dirfile,  $modeflags, $perms, $pagfilename;

C&lt;$basename&gt; is the base filename for the database.  The database is two
files with ".dir" and ".pag" extensions appended to C&lt;$basename&gt;,

    $basename.dir     (or .sdbm_dir on VMS, per DIRFEXT constant)
    $basename.pag

The two filenames can also be given separately in full as C&lt;$dirfile&gt;
and C&lt;$pagfilename&gt;.  This suits for two files without ".dir" and ".pag"
extensions, perhaps for example two files from L&lt;File::Temp&gt;.

C&lt;$modeflags&gt; can be the following constants from the C&lt;Fcntl&gt; module (in
the style of the L&lt;open(2)&gt; system call),

    O_RDONLY          read-only access
    O_WRONLY          write-only access
    O_RDWR            read and write access

If you want to create the file if it does not already exist then bitwise-OR
(C&lt;|&gt;) C&lt;O_CREAT&gt; too.  If you omit C&lt;O_CREAT&gt; and the database does not
already exist then the C&lt;tie&gt; call will fail.

    O_CREAT           create database if doesn't already exist

C&lt;$perms&gt; is the file permissions bits to use if new database files are
created.  This parameter is mandatory even when not creating a new database.
The permissions will be reduced by the user's umask so the usual value here
would be 0666, or if some very private data then 0600.  (See
L&lt;perlfunc/umask&gt;.)

=head1 EXPORTS

SDBM_File optionally exports the following constants:

=over

=item *

C&lt;PAGFEXT&gt; - the extension used for the page file, usually C&lt;.pag&gt;.

=item *

C&lt;DIRFEXT&gt; - the extension used for the directory file, C&lt;.dir&gt;
everywhere but VMS, where it is C&lt;.sdbm_dir&gt;.

=item *

C&lt;PAIRMAX&gt; - the maximum size of a stored hash entry, including the
length of both the key and value.

=back

These constants can also be used with fully qualified names,
eg. C&lt;SDBM_File::PAGFEXT&gt;.

=head1 DIAGNOSTICS

On failure, the C&lt;tie&gt; call returns an undefined value and probably
sets C&lt;$!&gt; to contain the reason the file could not be tied.

=head2 C&lt;sdbm store returned -1, errno 22, key "..." at ...&gt;

This warning is emitted when you try to store a key or a value that
is too long.  It means that the change was not recorded in the
database.  See BUGS AND WARNINGS below.

=head1 BUGS AND WARNINGS

There are a number of limits on the size of the data that you can
store in the SDBM file.  The most important is that the length of a
key, plus the length of its associated value, may not exceed 1008
bytes.

See L&lt;perlfunc/tie&gt;, L&lt;perldbmfilter&gt;, L&lt;Fcntl&gt;

=cut
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