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   1  package SDBM_File;
   2  
   3  use strict;
   4  use warnings;
   5  
   6  require Tie::Hash;
   7  use XSLoader ();
   8  
   9  our @ISA = qw(Tie::Hash);
  10  our $VERSION = "1.06";
  11  
  12  XSLoader::load 'SDBM_File', $VERSION;
  13  
  14  1;
  15  
  16  __END__
  17  
  18  =head1 NAME
  19  
  20  SDBM_File - Tied access to sdbm files
  21  
  22  =head1 SYNOPSIS
  23  
  24   use Fcntl;   # For O_RDWR, O_CREAT, etc.
  25   use SDBM_File;
  26  
  27   tie(%h, 'SDBM_File', 'filename', O_RDWR|O_CREAT, 0666)
  28     or die "Couldn't tie SDBM file 'filename': $!; aborting";
  29  
  30   # Now read and change the hash
  31   $h{newkey} = newvalue;
  32   print $h{oldkey}; 
  33   ...
  34  
  35   untie %h;
  36  
  37  =head1 DESCRIPTION
  38  
  39  C<SDBM_File> establishes a connection between a Perl hash variable and
  40  a file in SDBM_File format;.  You can manipulate the data in the file
  41  just as if it were in a Perl hash, but when your program exits, the
  42  data will remain in the file, to be used the next time your program
  43  runs.
  44  
  45  Use C<SDBM_File> with the Perl built-in C<tie> function to establish
  46  the connection between the variable and the file.  The arguments to
  47  C<tie> should be:
  48  
  49  =over 4
  50  
  51  =item 1.
  52  
  53  The hash variable you want to tie.
  54  
  55  =item 2. 
  56  
  57  The string C<"SDBM_File">.  (Ths tells Perl to use the C<SDBM_File>
  58  package to perform the functions of the hash.)
  59  
  60  =item 3. 
  61  
  62  The name of the file you want to tie to the hash.  
  63  
  64  =item 4.
  65  
  66  Flags.  Use one of:
  67  
  68  =over 2
  69  
  70  =item C<O_RDONLY>
  71  
  72  Read-only access to the data in the file.
  73  
  74  =item C<O_WRONLY>
  75  
  76  Write-only access to the data in the file.
  77  
  78  =item C<O_RDWR>
  79  
  80  Both read and write access.
  81  
  82  =back
  83  
  84  If you want to create the file if it does not exist, add C<O_CREAT> to
  85  any of these, as in the example.  If you omit C<O_CREAT> and the file
  86  does not already exist, the C<tie> call will fail.
  87  
  88  =item 5.
  89  
  90  The default permissions to use if a new file is created.  The actual
  91  permissions will be modified by the user's umask, so you should
  92  probably use 0666 here. (See L<perlfunc/umask>.)
  93  
  94  =back
  95  
  96  =head1 DIAGNOSTICS
  97  
  98  On failure, the C<tie> call returns an undefined value and probably
  99  sets C<$!> to contain the reason the file could not be tied.
 100  
 101  =head2 C<sdbm store returned -1, errno 22, key "..." at ...>
 102  
 103  This warning is emitted 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 SDBM 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.
 113  
 114  See L<perlfunc/tie>, L<perldbmfilter>, L<Fcntl>
 115  
 116  =cut