


ODBM_File(3p)    Perl Programmers Reference Guide   ODBM_File(3p)


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:

       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.)



perl v5.10.1                2008-09-29                          1





ODBM_File(3p)    Perl Programmers Reference Guide   ODBM_File(3p)


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








































perl v5.10.1                2008-09-29                          2


