| 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 = "1.05"; |
| 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 |