SDBM_File - Tied access to sdbm files

- NAME
- SYNOPSIS
- DESCRIPTION
- DIAGNOSTICS

- `sdbm store returned -1, errno 22, key "..." at ...`

- BUGS AND WARNINGS

# NAME

SDBM_File - Tied access to sdbm files

# SYNOPSIS

     use Fcntl;   # For O_RDWR, O_CREAT, etc.
     use SDBM_File;

     tie(%h, 'SDBM_File', 'filename', O_RDWR|O_CREAT, 0666)
       or die "Couldn't tie SDBM file 'filename': $!; aborting";

     # Now read and change the hash
     $h{newkey} = newvalue;
     print $h{oldkey};
     ...

     untie %h;

# DESCRIPTION

`SDBM_File` establishes a connection between a Perl hash variable and a file in SDBM_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 `SDBM_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 `"SDBM_File"`. (Ths tells Perl to use the `SDBM_File` package 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_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.

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 the perlfunc manpage.)

# DIAGNOSTICS

On failure, the `tie` call returns an undefined value and probably sets `$!` to contain the reason the file could not be tied.

## `sdbm store returned -1, errno 22, key "..." at ...`

This warning is emmitted 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 SDBM 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 the perlfunc manpage, the perldbmfilter manpage, the Fcntl manpage

SDBM_File - Tied access to sdbm files