ODBM_File(3p) Perl Programmers Reference Guide ODBM_File(3p)NAMEODBM_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 manipu-
late 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
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ODBM_File(3p) Perl Programmers Reference Guide ODBM_File(3p)
"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.
See "tie" in perlfunc, perldbmfilter, Fcntl
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