1package ODBM_File;
2
3use strict;
4use warnings;
5
6require Tie::Hash;
7require XSLoader;
8
9our @ISA = qw(Tie::Hash);
10our $VERSION = "1.16";
11
12XSLoader::load();
13
141;
15
16__END__
17
18=head1 NAME
19
20ODBM_File - Tied access to odbm files
21
22=head1 SYNOPSIS
23
24 use Fcntl;   # For O_RDWR, O_CREAT, etc.
25 use ODBM_File;
26
27  # Now read and change the hash
28  $h{newkey} = newvalue;
29  print $h{oldkey};
30  ...
31
32  untie %h;
33
34=head1 DESCRIPTION
35
36C<ODBM_File> establishes a connection between a Perl hash variable and
37a file in ODBM_File format;.  You can manipulate the data in the file
38just as if it were in a Perl hash, but when your program exits, the
39data will remain in the file, to be used the next time your program
40runs.
41
42Use C<ODBM_File> with the Perl built-in C<tie> function to establish
43the connection between the variable and the file.  The arguments to
44C<tie> should be:
45
46=over 4
47
48=item 1.
49
50The hash variable you want to tie.
51
52=item 2.
53
54The string C<"ODBM_File">.  (Ths tells Perl to use the C<ODBM_File>
55package to perform the functions of the hash.)
56
57=item 3.
58
59The name of the file you want to tie to the hash.
60
61=item 4.
62
63Flags.  Use one of:
64
65=over 2
66
67=item C<O_RDONLY>
68
69Read-only access to the data in the file.
70
71=item C<O_WRONLY>
72
73Write-only access to the data in the file.
74
75=item C<O_RDWR>
76
77Both read and write access.
78
79=back
80
81If you want to create the file if it does not exist, add C<O_CREAT> to
82any of these, as in the example.  If you omit C<O_CREAT> and the file
83does not already exist, the C<tie> call will fail.
84
85=item 5.
86
87The default permissions to use if a new file is created.  The actual
88permissions will be modified by the user's umask, so you should
89probably use 0666 here. (See L<perlfunc/umask>.)
90
91=back
92
93=head1 DIAGNOSTICS
94
95On failure, the C<tie> call returns an undefined value and probably
96sets C<$!> to contain the reason the file could not be tied.
97
98=head2 C<odbm store returned -1, errno 22, key "..." at ...>
99
100This warning is emitted when you try to store a key or a value that
101is too long.  It means that the change was not recorded in the
102database.  See BUGS AND WARNINGS below.
103
104=head1 SECURITY AND PORTABILITY
105
106B<Do not accept ODBM files from untrusted sources.>
107
108On modern Linux systems these are typically GDBM files, which are not
109portable across platforms.
110
111The GDBM documentation doesn't imply that files from untrusted sources
112can be safely used with C<libgdbm>.
113
114Systems that don't use GDBM compatibilty for old dbm support will be
115using a platform specific library, possibly inherited from BSD
116systems, where it may or may not be safe to use an untrusted file.
117
118A maliciously crafted file might cause perl to crash or even expose a
119security vulnerability.
120
121=head1 BUGS AND WARNINGS
122
123There are a number of limits on the size of the data that you can
124store in the ODBM file.  The most important is that the length of a
125key, plus the length of its associated value, may not exceed 1008
126bytes.
127
128See L<perlfunc/tie>, L<perldbmfilter>, L<Fcntl>
129
130=cut
131