1NDBM_File(3pm)         Perl Programmers Reference Guide         NDBM_File(3pm)
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NAME

6       NDBM_File - Tied access to ndbm files
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SYNOPSIS

9         use Fcntl;   # For O_RDWR, O_CREAT, etc.
10         use NDBM_File;
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12         tie(%h, 'NDBM_File', 'filename', O_RDWR|O_CREAT, 0666)
13           or die "Couldn't tie NDBM file 'filename': $!; aborting";
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15         # Now read and change the hash
16         $h{newkey} = newvalue;
17         print $h{oldkey};
18         ...
19
20         untie %h;
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DESCRIPTION

23       "NDBM_File" establishes a connection between a Perl hash variable and a
24       file in NDBM_File format;.  You can manipulate the data in the file
25       just as if it were in a Perl hash, but when your program exits, the
26       data will remain in the file, to be used the next time your program
27       runs.
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29       Use "NDBM_File" with the Perl built-in "tie" function to establish the
30       connection between the variable and the file.  The arguments to "tie"
31       should be:
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33       1.  The hash variable you want to tie.
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35       2.  The string "NDBM_File".  (Ths tells Perl to use the "NDBM_File"
36           package to perform the functions of the hash.)
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38       3.  The name of the file you want to tie to the hash.
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40       4.  Flags.  Use one of:
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42           "O_RDONLY"
43             Read-only access to the data in the file.
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45           "O_WRONLY"
46             Write-only access to the data in the file.
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48           "O_RDWR"
49             Both read and write access.
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51           If you want to create the file if it does not exist, add "O_CREAT"
52           to any of these, as in the example.  If you omit "O_CREAT" and the
53           file does not already exist, the "tie" call will fail.
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55       5.  The default permissions to use if a new file is created.  The
56           actual permissions will be modified by the user's umask, so you
57           should probably use 0666 here. (See "umask" in perlfunc.)
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DIAGNOSTICS

60       On failure, the "tie" call returns an undefined value and probably sets
61       $! to contain the reason the file could not be tied.
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63   "ndbm store returned -1, errno 22, key "..." at ..."
64       This warning is emitted when you try to store a key or a value that is
65       too long.  It means that the change was not recorded in the database.
66       See BUGS AND WARNINGS below.
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BUGS AND WARNINGS

69       There are a number of limits on the size of the data that you can store
70       in the NDBM file.  The most important is that the length of a key, plus
71       the length of its associated value, may not exceed 1008 bytes.
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73       See "tie" in perlfunc, perldbmfilter, Fcntl
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77perl v5.12.4                      2011-06-07                    NDBM_File(3pm)
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