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1 | package SDBM_File; |
2 | |
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3 | use strict; |
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4 | |
5 | require Tie::Hash; |
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6 | use XSLoader (); |
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7 | |
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8 | our @ISA = qw(Tie::Hash); |
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9 | our $VERSION = "1.03" ; |
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10 | |
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11 | XSLoader::load 'SDBM_File', $VERSION; |
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12 | |
13 | 1; |
14 | |
15 | __END__ |
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16 | |
17 | =head1 NAME |
18 | |
19 | SDBM_File - Tied access to sdbm files |
20 | |
21 | =head1 SYNOPSIS |
22 | |
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23 | use Fcntl; # For O_RDWR, O_CREAT, etc. |
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24 | use SDBM_File; |
25 | |
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26 | tie(%h, 'SDBM_File', 'filename', O_RDWR|O_CREAT, 0666) |
27 | or die "Couldn't tie SDBM file 'filename': $!; aborting"; |
28 | |
29 | # Now read and change the hash |
30 | $h{newkey} = newvalue; |
31 | print $h{oldkey}; |
32 | ... |
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33 | |
34 | untie %h; |
35 | |
36 | =head1 DESCRIPTION |
37 | |
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38 | C<SDBM_File> establishes a connection between a Perl hash variable and |
39 | a file in SDBM_File format;. You can manipulate the data in the file |
40 | just as if it were in a Perl hash, but when your program exits, the |
41 | data will remain in the file, to be used the next time your program |
42 | runs. |
43 | |
44 | Use C<SDBM_File> with the Perl built-in C<tie> function to establish |
45 | the connection between the variable and the file. The arguments to |
46 | C<tie> should be: |
47 | |
48 | =over 4 |
49 | |
50 | =item 1. |
51 | |
52 | The hash variable you want to tie. |
53 | |
54 | =item 2. |
55 | |
56 | The string C<"SDBM_File">. (Ths tells Perl to use the C<SDBM_File> |
57 | package to perform the functions of the hash.) |
58 | |
59 | =item 3. |
60 | |
61 | The name of the file you want to tie to the hash. |
62 | |
63 | =item 4. |
64 | |
65 | Flags. Use one of: |
66 | |
67 | =over 2 |
68 | |
69 | =item C<O_RDONLY> |
70 | |
71 | Read-only access to the data in the file. |
72 | |
73 | =item C<O_WRONLY> |
74 | |
75 | Write-only access to the data in the file. |
76 | |
77 | =item C<O_RDWR> |
78 | |
79 | Both read and write access. |
80 | |
81 | =back |
82 | |
83 | If you want to create the file if it does not exist, add C<O_CREAT> to |
84 | any of these, as in the example. If you omit C<O_CREAT> and the file |
85 | does not already exist, the C<tie> call will fail. |
86 | |
87 | =item 5. |
88 | |
89 | The default permissions to use if a new file is created. The actual |
90 | permissions will be modified by the user's umask, so you should |
91 | probably use 0666 here. (See L<perlfunc/umask>.) |
92 | |
93 | =back |
94 | |
95 | =head1 DIAGNOSTICS |
96 | |
97 | On failure, the C<tie> call returns an undefined value and probably |
98 | sets C<$!> to contain the reason the file could not be tied. |
99 | |
100 | =head2 C<sdbm store returned -1, errno 22, key "..." at ...> |
101 | |
102 | This warning is emmitted when you try to store a key or a value that |
103 | is too long. It means that the change was not recorded in the |
104 | database. See BUGS AND WARNINGS below. |
105 | |
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106 | =head1 BUGS AND WARNINGS |
107 | |
108 | There are a number of limits on the size of the data that you can |
109 | store in the SDBM file. The most important is that the length of a |
110 | key, plus the length of its associated value, may not exceed 1008 |
111 | bytes. |
112 | |
113 | See L<perlfunc/tie>, L<perldbmfilter>, L<Fcntl> |
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114 | |
115 | =cut |