.\" -*- mode: troff; coding: utf-8 -*-
.\" Automatically generated by Pod::Man v6.0.2 (Pod::Simple 3.45)
.\"
.\" Standard preamble:
.\" ========================================================================
.de Sp \" Vertical space (when we can't use .PP)
.if t .sp .5v
.if n .sp
..
.de Vb \" Begin verbatim text
.ft CW
.nf
.ne \\$1
..
.de Ve \" End verbatim text
.ft R
.fi
..
.\" \*(C` and \*(C' are quotes in nroff, nothing in troff, for use with C<>.
.ie n \{\
.    ds C` ""
.    ds C' ""
'br\}
.el\{\
.    ds C`
.    ds C'
'br\}
.\"
.\" Escape single quotes in literal strings from groff's Unicode transform.
.ie \n(.g .ds Aq \(aq
.el       .ds Aq '
.\"
.\" If the F register is >0, we'll generate index entries on stderr for
.\" titles (.TH), headers (.SH), subsections (.SS), items (.Ip), and index
.\" entries marked with X<> in POD.  Of course, you'll have to process the
.\" output yourself in some meaningful fashion.
.\"
.\" Avoid warning from groff about undefined register 'F'.
.de IX
..
.nr rF 0
.if \n(.g .if rF .nr rF 1
.if (\n(rF:(\n(.g==0)) \{\
.    if \nF \{\
.        de IX
.        tm Index:\\$1\t\\n%\t"\\$2"
..
.        if !\nF==2 \{\
.            nr % 0
.            nr F 2
.        \}
.    \}
.\}
.rr rF
.\"
.\" Required to disable full justification in groff 1.23.0.
.if n .ds AD l
.\" ========================================================================
.\"
.IX Title "ODBM_File 3"
.TH ODBM_File 3 2025-06-24 "perl v5.42.0" "Perl Programmers Reference Guide"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH NAME
ODBM_File \- Tied access to odbm files
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 2
\& use Fcntl;   # For O_RDWR, O_CREAT, etc.
\& use ODBM_File;
\&
\& tie(%h, \*(AqODBM_File\*(Aq, \*(Aqfilename.dbmx\*(Aq, O_RDWR|O_CREAT, 0640)
\&   or die "Couldn\*(Aqt tie ODBM file \*(Aqfilename.dbmx\*(Aq: $!; aborting";
\&
\& # Now read and change the hash
\& $h{newkey} = newvalue;
\& print $h{oldkey};
\& ...
\&
\& untie %h;
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
\&\f(CW\*(C`ODBM_File\*(C'\fR establishes a connection between a Perl hash variable and
a file in ODBM_File format;.  You can manipulate the data in the file
just as if it were in a Perl hash, but when your program exits, the
data will remain in the file, to be used the next time your program
runs.
.PP
Use \f(CW\*(C`ODBM_File\*(C'\fR with the Perl built\-in \f(CW\*(C`tie\*(C'\fR function to establish
the connection between the variable and the file.  The arguments to
\&\f(CW\*(C`tie\*(C'\fR should be:
.IP 1. 4
The hash variable you want to tie.
.IP 2. 4
The string \f(CW"ODBM_File"\fR.  (Ths tells Perl to use the \f(CW\*(C`ODBM_File\*(C'\fR
package to perform the functions of the hash.)
.IP 3. 4
The name of the file you want to tie to the hash.
.IP 4. 4
Flags.  Use one of:
.RS 4
.ie n .IP """O_RDONLY""" 2
.el .IP \f(CWO_RDONLY\fR 2
.IX Item "O_RDONLY"
Read\-only access to the data in the file.
.ie n .IP """O_WRONLY""" 2
.el .IP \f(CWO_WRONLY\fR 2
.IX Item "O_WRONLY"
Write\-only access to the data in the file.
.ie n .IP """O_RDWR""" 2
.el .IP \f(CWO_RDWR\fR 2
.IX Item "O_RDWR"
Both read and write access.
.RE
.RS 4
.Sp
If you want to create the file if it does not exist, add \f(CW\*(C`O_CREAT\*(C'\fR to
any of these, as in the example.  If you omit \f(CW\*(C`O_CREAT\*(C'\fR and the file
does not already exist, the \f(CW\*(C`tie\*(C'\fR call will fail.
.RE
.IP 5. 4
The default permissions to use if a new file is created.  The actual
permissions will be modified by the user\*(Aqs umask, so you should
probably use 0666 here. (See "umask" in perlfunc.)
.SH DIAGNOSTICS
.IX Header "DIAGNOSTICS"
On failure, the \f(CW\*(C`tie\*(C'\fR call returns an undefined value and probably
sets \f(CW$!\fR to contain the reason the file could not be tied.
.ie n .SS """odbm store returned \-1, errno 22, key ""..."" at ..."""
.el .SS "\f(CWodbm store returned \-1, errno 22, key ""..."" at ...\fP"
.IX Subsection "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.
.SH "SECURITY AND PORTABILITY"
.IX Header "SECURITY AND PORTABILITY"
\&\fBDo not accept ODBM files from untrusted sources.\fR
.PP
On modern Linux systems these are typically GDBM files, which are not
portable across platforms.
.PP
The GDBM documentation doesn\*(Aqt imply that files from untrusted sources
can be safely used with \f(CW\*(C`libgdbm\*(C'\fR.
.PP
Systems that don\*(Aqt 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.
.PP
A maliciously crafted file might cause perl to crash or even expose a
security vulnerability.
.SH "BUGS AND WARNINGS"
.IX Header "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.
.PP
See "tie" in perlfunc, perldbmfilter, Fcntl