NAME
ODBM_File - Tied access to odbm files
SYNOPSIS
use Fcntl; # For O_RDWR, O_CREAT, etc.
use ODBM_File;
# Now read and change the hash
$h{newkey} = newvalue;
print $h{oldkey};
...
untie %h;DESCRIPTION
ODBM_File establishes a connection between a Perl hash variable and a file in ODBM_File format;. You can manipulate the data in the file just as if it were in a Perl hash, but when your program exits, the data will remain in the file, to be used the next time your program runs.
Use ODBM_File with the Perl built-in tie function to establish the connection between the variable and the file. The arguments to tie should be:
The hash variable you want to tie.
The string
"ODBM_File". (Ths tells Perl to use theODBM_Filepackage to perform the functions of the hash.)The name of the file you want to tie to the hash.
Flags. Use one of:
O_RDONLY-
Read-only access to the data in the file.
O_WRONLY-
Write-only access to the data in the file.
O_RDWR-
Both read and write access.
If you want to create the file if it does not exist, add
O_CREATto any of these, as in the example. If you omitO_CREATand the file does not already exist, thetiecall will fail.The default permissions to use if a new file is created. The actual permissions will be modified by the user's umask, so you should probably use 0666 here. (See "umask" in perlfunc.)
DIAGNOSTICS
On failure, the tie call returns an undefined value and probably sets $! to contain the reason the file could not be tied.
odbm store returned -1, errno 22, key "..." at ...
This warning is emitted when you try to store a key or a value that is too long. It means that the change was not recorded in the database. See BUGS AND WARNINGS below.
BUGS AND WARNINGS
There are a number of limits on the size of the data that you can store in the ODBM file. The most important is that the length of a key, plus the length of its associated value, may not exceed 1008 bytes.