NAME¶

NDBM_File - Tied access to ndbm files

SYNOPSIS¶

  use Fcntl;   # For O_RDWR, O_CREAT, etc.
  use NDBM_File;
  tie(%h, 'NDBM_File', 'filename', O_RDWR|O_CREAT, 0666)
    or die "Couldn't tie NDBM file 'filename': $!; aborting";
  # Now read and change the hash
  $h{newkey} = newvalue;
  print $h{oldkey};
  ...
  untie %h;

DESCRIPTION¶

"NDBM_File" establishes a connection between a Perl hash variable and a file in NDBM_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 "NDBM_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 "NDBM_File". (Ths tells Perl to use the "NDBM_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:

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.

BUGS AND WARNINGS¶

There are a number of limits on the size of the data that you can store in the NDBM 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