1ODBM_File(3pm) Perl Programmers Reference Guide ODBM_File(3pm)
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6 ODBM_File - Tied access to odbm files
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9 use Fcntl; # For O_RDWR, O_CREAT, etc.
10 use ODBM_File;
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12 # Now read and change the hash
13 $h{newkey} = newvalue;
14 print $h{oldkey};
15 ...
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17 untie %h;
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20 "ODBM_File" establishes a connection between a Perl hash variable and a
21 file in ODBM_File format;. You can manipulate the data in the file
22 just as if it were in a Perl hash, but when your program exits, the
23 data will remain in the file, to be used the next time your program
24 runs.
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26 Use "ODBM_File" with the Perl built-in "tie" function to establish the
27 connection between the variable and the file. The arguments to "tie"
28 should be:
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30 1. The hash variable you want to tie.
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32 2. The string "ODBM_File". (Ths tells Perl to use the "ODBM_File"
33 package to perform the functions of the hash.)
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35 3. The name of the file you want to tie to the hash.
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37 4. Flags. Use one of:
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39 "O_RDONLY"
40 Read-only access to the data in the file.
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42 "O_WRONLY"
43 Write-only access to the data in the file.
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45 "O_RDWR"
46 Both read and write access.
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48 If you want to create the file if it does not exist, add "O_CREAT"
49 to any of these, as in the example. If you omit "O_CREAT" and the
50 file does not already exist, the "tie" call will fail.
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52 5. The default permissions to use if a new file is created. The
53 actual permissions will be modified by the user's umask, so you
54 should probably use 0666 here. (See "umask" in perlfunc.)
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57 On failure, the "tie" call returns an undefined value and probably sets
58 $! to contain the reason the file could not be tied.
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60 "odbm store returned -1, errno 22, key "..." at ..."
61 This warning is emitted when you try to store a key or a value that is
62 too long. It means that the change was not recorded in the database.
63 See BUGS AND WARNINGS below.
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66 There are a number of limits on the size of the data that you can store
67 in the ODBM file. The most important is that the length of a key, plus
68 the length of its associated value, may not exceed 1008 bytes.
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70 See "tie" in perlfunc, perldbmfilter, Fcntl
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74perl v5.28.2 2018-11-01 ODBM_File(3pm)