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<title>8.6 dbm -- Simple ``database'' interface
</title>
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<H1><A NAME=
"SECTION0010600000000000000000">
8.6 <tt class=
"module">dbm
</tt> --
Simple ``database'' interface
</A>
<A NAME=
"module-dbm"></A>
<p class=
"availability">Availability:
<span
class=
"platform">Unix
</span>.
</p>
The
<tt class=
"module">dbm
</tt> module provides an interface to the
<span class=
"Unix">Unix
</span>
(
<code>n
</code>)
<code>dbm
</code> library. Dbm objects behave like mappings
(dictionaries), except that keys and values are always strings.
Printing a dbm object doesn't print the keys and values, and the
<tt class=
"method">items()
</tt> and
<tt class=
"method">values()
</tt> methods are not supported.
This module can be used with the ``classic'' ndbm interface, the BSD
DB compatibility interface, or the GNU GDBM compatibility interface.
On
<span class=
"Unix">Unix
</span>, the
<b class=
"program">configure
</b> script will attempt to locate the
appropriate header file to simplify building this module.
The module defines the following:
<dl><dt><b><span class=
"typelabel">exception
</span> <tt id='l2h-
2996' xml:id='l2h-
2996'
class=
"exception">error
</tt></b></dt>
Raised on dbm-specific errors, such as I/O errors.
<tt class=
"exception">KeyError
</tt> is raised for general mapping errors like
specifying an incorrect key.
<dl><dt><b><tt id='l2h-
2997' xml:id='l2h-
2997'
>library
</tt></b></dt>
Name of the
<code>ndbm
</code> implementation library used.
<dl><dt><table cellpadding=
"0" cellspacing=
"0"><tr valign=
"baseline">
<td><nobr><b><tt id='l2h-
2998' xml:id='l2h-
2998'
class=
"function">open
</tt></b>(
</nobr></td>
<td><var>filename
</var><big>[
</big><var>, flag
</var><big>[
</big><var>, mode
</var><big>]
</big><var></var><big>]
</big><var></var>)
</td></tr></table></dt>
Open a dbm database and return a dbm object. The
<var>filename
</var>
argument is the name of the database file (without the
<span class=
"file">.dir
</span> or
<span class=
"file">.pag
</span> extensions; note that the BSD DB implementation of the
interface will append the extension
<span class=
"file">.db
</span> and only create one
The optional
<var>flag
</var> argument must be one of these values:
<div class=
"center"><table class=
"realtable">
<th class=
"center">Value
</th>
<th class=
"left" >Meaning
</th>
<tr><td class=
"center" valign=
"baseline"><code>'r'
</code></td>
<td class=
"left" >Open existing database for reading only (default)
</td></tr>
<tr><td class=
"center" valign=
"baseline"><code>'w'
</code></td>
<td class=
"left" >Open existing database for reading and writing
</td></tr>
<tr><td class=
"center" valign=
"baseline"><code>'c'
</code></td>
<td class=
"left" >Open database for reading and writing, creating it if
it doesn't exist
</td></tr>
<tr><td class=
"center" valign=
"baseline"><code>'n'
</code></td>
<td class=
"left" >Always create a new, empty database, open for reading
and writing
</td></tr></tbody>
The optional
<var>mode
</var> argument is the
<span class=
"Unix">Unix
</span> mode of the file, used
only when the database has to be created. It defaults to octal
<p class=
"heading">See Also:
</p>
<dl compact=
"compact" class=
"seemodule">
<dt>Module
<b><tt class=
"module"><a href=
"module-anydbm.html">anydbm
</a></tt>:
</b>
<dd>Generic interface to
<code>dbm
</code>-style databases.
<dl compact=
"compact" class=
"seemodule">
<dt>Module
<b><tt class=
"module"><a href=
"module-gdbm.html">gdbm
</a></tt>:
</b>
<dd>Similar interface to the GNU GDBM library.
<dl compact=
"compact" class=
"seemodule">
<dt>Module
<b><tt class=
"module"><a href=
"module-whichdb.html">whichdb
</a></tt>:
</b>
<dd>Utility module used to determine the type of an
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<span class=
"release-info">Release
2.4.2, documentation updated on
28 September
2005.
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