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1 | package NDBM_File; |
2 | |
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3 | BEGIN { |
4 | if ($] >= 5.002) { |
5 | use strict; |
6 | } |
7 | } |
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8 | |
9 | require Tie::Hash; |
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10 | use XSLoader (); |
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11 | |
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12 | our @ISA = qw(Tie::Hash); |
13 | our $VERSION = "1.03"; |
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14 | |
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15 | XSLoader::load 'NDBM_File', $VERSION; |
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16 | |
17 | 1; |
18 | |
19 | __END__ |
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20 | |
21 | =head1 NAME |
22 | |
23 | NDBM_File - Tied access to ndbm files |
24 | |
25 | =head1 SYNOPSIS |
26 | |
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27 | use Fcntl; # For O_RDWR, O_CREAT, etc. |
28 | use NDBM_File; |
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29 | |
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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 | |
39 | C<NDBM_File> establishes a connection between a Perl hash variable and |
40 | a file in NDBM_File format;. You can manipulate the data in the file |
41 | just as if it were in a Perl hash, but when your program exits, the |
42 | data will remain in the file, to be used the next time your program |
43 | runs. |
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44 | |
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45 | Use C<NDBM_File> with the Perl built-in C<tie> function to establish |
46 | the connection between the variable and the file. The arguments to |
47 | C<tie> should be: |
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48 | |
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49 | =over 4 |
50 | |
51 | =item 1. |
52 | |
53 | The hash variable you want to tie. |
54 | |
55 | =item 2. |
56 | |
57 | The string C<"NDBM_File">. (Ths tells Perl to use the C<NDBM_File> |
58 | package to perform the functions of the hash.) |
59 | |
60 | =item 3. |
61 | |
62 | The name of the file you want to tie to the hash. |
63 | |
64 | =item 4. |
65 | |
66 | Flags. Use one of: |
67 | |
68 | =over 2 |
69 | |
70 | =item C<O_RDONLY> |
71 | |
72 | Read-only access to the data in the file. |
73 | |
74 | =item C<O_WRONLY> |
75 | |
76 | Write-only access to the data in the file. |
77 | |
78 | =item C<O_RDWR> |
79 | |
80 | Both read and write access. |
81 | |
82 | =back |
83 | |
84 | If you want to create the file if it does not exist, add C<O_CREAT> to |
85 | any of these, as in the example. If you omit C<O_CREAT> and the file |
86 | does not already exist, the C<tie> call will fail. |
87 | |
88 | =item 5. |
89 | |
90 | The default permissions to use if a new file is created. The actual |
91 | permissions will be modified by the user's umask, so you should |
92 | probably use 0666 here. (See L<perlfunc/umask>.) |
93 | |
94 | =back |
95 | |
96 | =head1 DIAGNOSTICS |
97 | |
98 | On failure, the C<tie> call returns an undefined value and probably |
99 | sets C<$!> to contain the reason the file could not be tied. |
100 | |
101 | =head2 C<ndbm store returned -1, errno 22, key "..." at ...> |
102 | |
103 | This warning is emmitted when you try to store a key or a value that |
104 | is too long. It means that the change was not recorded in the |
105 | database. See BUGS AND WARNINGS below. |
106 | |
107 | =head1 BUGS AND WARNINGS |
108 | |
109 | There are a number of limits on the size of the data that you can |
110 | store in the NDBM file. The most important is that the length of a |
111 | key, plus the length of its associated value, may not exceed 1008 |
112 | bytes. |
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113 | |
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114 | See L<perlfunc/tie>, L<perldbmfilter>, L<Fcntl> |
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115 | |
116 | =cut |