1package NDBM_File;
2
3use strict;
4use warnings;
5
6require Tie::Hash;
7require XSLoader;
8
9our @ISA = qw(Tie::Hash);
10our $VERSION = "1.12";
11
12XSLoader::load();
13
141;
15
16__END__
17
18=head1 NAME
19
20NDBM_File - Tied access to ndbm files
21
22=head1 SYNOPSIS
23
24  use Fcntl;   # For O_RDWR, O_CREAT, etc.
25  use NDBM_File;
26
27  tie(%h, 'NDBM_File', 'filename', O_RDWR|O_CREAT, 0666)
28    or die "Couldn't tie NDBM file 'filename': $!; aborting";
29
30  # Now read and change the hash
31  $h{newkey} = newvalue;
32  print $h{oldkey};
33  ...
34
35  untie %h;
36
37=head1 DESCRIPTION
38
39C<NDBM_File> establishes a connection between a Perl hash variable and
40a file in NDBM_File format;.  You can manipulate the data in the file
41just as if it were in a Perl hash, but when your program exits, the
42data will remain in the file, to be used the next time your program
43runs.
44
45Use C<NDBM_File> with the Perl built-in C<tie> function to establish
46the connection between the variable and the file.  The arguments to
47C<tie> should be:
48
49=over 4
50
51=item 1.
52
53The hash variable you want to tie.
54
55=item 2.
56
57The string C<"NDBM_File">.  (Ths tells Perl to use the C<NDBM_File>
58package to perform the functions of the hash.)
59
60=item 3.
61
62The name of the file you want to tie to the hash.
63
64=item 4.
65
66Flags.  Use one of:
67
68=over 2
69
70=item C<O_RDONLY>
71
72Read-only access to the data in the file.
73
74=item C<O_WRONLY>
75
76Write-only access to the data in the file.
77
78=item C<O_RDWR>
79
80Both read and write access.
81
82=back
83
84If you want to create the file if it does not exist, add C<O_CREAT> to
85any of these, as in the example.  If you omit C<O_CREAT> and the file
86does not already exist, the C<tie> call will fail.
87
88=item 5.
89
90The default permissions to use if a new file is created.  The actual
91permissions will be modified by the user's umask, so you should
92probably use 0666 here. (See L<perlfunc/umask>.)
93
94=back
95
96=head1 DIAGNOSTICS
97
98On failure, the C<tie> call returns an undefined value and probably
99sets C<$!> to contain the reason the file could not be tied.
100
101=head2 C<ndbm store returned -1, errno 22, key "..." at ...>
102
103This warning is emitted when you try to store a key or a value that
104is too long.  It means that the change was not recorded in the
105database.  See BUGS AND WARNINGS below.
106
107=head1 BUGS AND WARNINGS
108
109There are a number of limits on the size of the data that you can
110store in the NDBM file.  The most important is that the length of a
111key, plus the length of its associated value, may not exceed 1008
112bytes.
113
114See L<perlfunc/tie>, L<perldbmfilter>, L<Fcntl>
115
116=cut
117