---
name: "ODBM_File"
section: "3perl"
platform: "linux"
package: "perl"
version: "5.44.0-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/ODBM_File"
---

# ODBM\_File(3perl)

Tied access to odbm files

## NAME

ODBM\_File - Tied access to odbm files

## SYNOPSIS

```
 use Fcntl;   # For O_RDWR, O_CREAT, etc.
 use ODBM_File;
 tie(%h, 'ODBM_File', 'filename.dbmx', O_RDWR|O_CREAT, 0640)
   or die "Couldn't tie ODBM file 'filename.dbmx': $!; aborting";
 # 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.  See BUGS AND WARNINGS below.

## SECURITY AND PORTABILITY

**Do not accept ODBM files from untrusted sources.**

On modern Linux systems these are typically GDBM files, which are not portable across platforms.

The GDBM documentation doesn't imply that files from untrusted sources can be safely used with `"libgdbm"`.

Systems that don't use GDBM compatibility for old dbm support will be using a platform specific library, possibly inherited from BSD systems, where it may or may not be safe to use an untrusted file.

A maliciously crafted file might cause perl to crash or even expose a security vulnerability.

## 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