ODBM_File (3)
Leading comments
Automatically generated by Pod::Man 4.09 (Pod::Simple 3.35) Standard preamble: ========================================================================
NAME
ODBM_File - Tied access to odbm filesSYNOPSIS
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:
- 1.
- The hash variable you want to tie.
- 2.
- The string "ODBM_File". (Ths tells Perl to use the "ODBM_File" package to perform the functions of the hash.)
- 3.
- The name of the file you want to tie to the hash.
- 4.
-
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_CREAT" to any of these, as in the example. If you omit "O_CREAT" and the file does not already exist, the "tie" call will fail.
-
- 5.
- 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. SeeBUGS AND WARNINGS
below.
BUGS AND WARNINGS
There are a number of limits on the size of the data that you can store in theODBM
file. The most important is that the length of a
key, plus the length of its associated value, may not exceed 1008
bytes.
See ``tie'' in perlfunc, perldbmfilter, Fcntl