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<H1><A NAME="SECTION0010600000000000000000">
8.6 <tt class="module">dbm</tt> --
         Simple ``database'' interface</A>
</H1>

<P>
<A NAME="module-dbm"></A>  
<p class="availability">Availability: <span
 class="platform">Unix</span>.</p>

<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.

<P>
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.

<P>
The module defines the following:

<P>
<dl><dt><b><span class="typelabel">exception</span>&nbsp;<tt id='l2h-2996' xml:id='l2h-2996' class="exception">error</tt></b></dt>
<dd>
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.
</dd></dl>

<P>
<dl><dt><b><tt id='l2h-2997' xml:id='l2h-2997'>library</tt></b></dt>
<dd>
Name of the <code>ndbm</code> implementation library used.
</dd></dl>

<P>
<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>
<dd>
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
file).

<P>
The optional <var>flag</var> argument must be one of these values:

<P>
<div class="center"><table class="realtable">
  <thead>
    <tr>
      <th class="center">Value</th>
      <th class="left"  >Meaning</th>
      </tr>
    </thead>
  <tbody>
    <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>
</table></div>

<P>
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
<code>0666</code>.
</dl>

<P>
<div class="seealso">
  <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>
  <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>
  <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
                      existing database.
  </dl>
</div>

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	54
	55	<H1><A NAME="SECTION0010600000000000000000">
	56	8.6 <tt class="module">dbm</tt> --
	57	Simple ``database'' interface</A>
	58	</H1>
	59
	60	<P>
	61	<A NAME="module-dbm"></A>
	62	<p class="availability">Availability: <span
	63	class="platform">Unix</span>.</p>
	64
65	<P>
66	The <tt class="module">dbm</tt> module provides an interface to the <span class="Unix">Unix</span>
67	(<code>n</code>)<code>dbm</code> library. Dbm objects behave like mappings
68	(dictionaries), except that keys and values are always strings.
69	Printing a dbm object doesn't print the keys and values, and the
70	<tt class="method">items()</tt> and <tt class="method">values()</tt> methods are not supported.
71
72	<P>
73	This module can be used with the ``classic'' ndbm interface, the BSD
74	DB compatibility interface, or the GNU GDBM compatibility interface.
75	On <span class="Unix">Unix</span>, the <b class="program">configure</b> script will attempt to locate the
76	appropriate header file to simplify building this module.
77
78	<P>
79	The module defines the following:
80
81	<P>
82	<dl><dt><b><span class="typelabel">exception</span> <tt id='l2h-2996' xml:id='l2h-2996' class="exception">error</tt></b></dt>
83	<dd>
84	Raised on dbm-specific errors, such as I/O errors.
85	<tt class="exception">KeyError</tt> is raised for general mapping errors like
86	specifying an incorrect key.
87	</dd></dl>
88
89	<P>
90	<dl><dt><b><tt id='l2h-2997' xml:id='l2h-2997'>library</tt></b></dt>
91	<dd>
92	Name of the <code>ndbm</code> implementation library used.
93	</dd></dl>
94
95	<P>
96	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
97	<td><nobr><b><tt id='l2h-2998' xml:id='l2h-2998' class="function">open</tt></b>(</nobr></td>
98	<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>
99	<dd>
100	Open a dbm database and return a dbm object. The <var>filename</var>
101	argument is the name of the database file (without the <span class="file">.dir</span> or
102	<span class="file">.pag</span> extensions; note that the BSD DB implementation of the
103	interface will append the extension <span class="file">.db</span> and only create one
104	file).
105
106	<P>
107	The optional <var>flag</var> argument must be one of these values:
108
109	<P>
110	<div class="center"><table class="realtable">
111	<thead>
112	<tr>
113	<th class="center">Value</th>
114	<th class="left" >Meaning</th>
115	</tr>
116	</thead>
117	<tbody>
118	<tr><td class="center" valign="baseline"><code>'r'</code></td>
119	<td class="left" >Open existing database for reading only (default)</td></tr>
120	<tr><td class="center" valign="baseline"><code>'w'</code></td>
121	<td class="left" >Open existing database for reading and writing</td></tr>
122	<tr><td class="center" valign="baseline"><code>'c'</code></td>
123	<td class="left" >Open database for reading and writing, creating it if
124	it doesn't exist</td></tr>
125	<tr><td class="center" valign="baseline"><code>'n'</code></td>
126	<td class="left" >Always create a new, empty database, open for reading
127	and writing</td></tr></tbody>
128	</table></div>
129
130	<P>
131	The optional <var>mode</var> argument is the <span class="Unix">Unix</span> mode of the file, used
132	only when the database has to be created. It defaults to octal
133	<code>0666</code>.
134	</dl>
135
136	<P>
137	<div class="seealso">
138	<p class="heading">See Also:</p>
139
140	<dl compact="compact" class="seemodule">
141	<dt>Module <b><tt class="module"><a href="module-anydbm.html">anydbm</a></tt>:</b>
142	<dd>Generic interface to <code>dbm</code>-style databases.
143	</dl>
144	<dl compact="compact" class="seemodule">
145	<dt>Module <b><tt class="module"><a href="module-gdbm.html">gdbm</a></tt>:</b>
146	<dd>Similar interface to the GNU GDBM library.
147	</dl>
148	<dl compact="compact" class="seemodule">
149	<dt>Module <b><tt class="module"><a href="module-whichdb.html">whichdb</a></tt>:</b>
150	<dd>Utility module used to determine the type of an
151	existing database.
152	</dl>
153	</div>
154
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