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cdb: cdbmake</title>
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<div class=pagetitle>cdb: cdbmake</div>
<h3>NAME</h3>
<p>cdbmake - create a constant database</p>
<h3>SYNOPSIS</h3>
<p><code>cdbmake</code> <em>f</em> <em>ftmp</em></p>
<h3>DESCRIPTION</h3>
<p><code>cdbmake</code> reads a series of encoded records from its standard input
and writes a constant database to a file named <em>f</em>,
replacing any previous contents of <em>f</em>.</p>
<p><code>cdbmake</code> ensures that <em>f</em> is updated atomically,
so programs reading <em>f</em> never have to wait for <code>cdbmake</code> to finish.
It does this by first writing the database to <em>ftmp</em>
and then moving <em>ftmp</em> on top of <em>f</em>.
If <em>ftmp</em> already exists, it is destroyed.
The directories containing <em>ftmp</em> and <em>f</em> must be writable to <code>cdbmake</code>;
they must also be on the same filesystem.</p>
<p><code>cdbmake</code> always makes sure that <em>ftmp</em> is safely written to disk
before it replaces <em>f</em>.
If the input is in a bad format
or if <code>cdbmake</code> has any trouble writing <em>ftmp</em> to disk,
<code>cdbmake</code> complains and leaves f alone.</p>
<p>There is also a <code>cdb64make</code> that uses cdb64 format instead of cdb format.</p>
<h3>RECORD FORMAT</h3>
<p>Records are indexed by keys.
A key is a string.
The file <em>f</em> is structured
so that another program,
starting from a key,
can quickly find the relevant record.
<code>cdbmake</code> allows several records with the same key, although</p>
<ul>
<li>
<p>most readers take only the first record, and</p>
</li>
<li>
<p><code>cdbmake</code> slows down somewhat if there are many records with the same key.</p>
</li>
</ul>
<p><code>cdbmake</code> preserves the order of records.</p>
<p>For the input provided to <code>cdbmake</code>,
each record is encoded
as +<em>klen</em>,<em>dlen</em>:<em>key</em>-><em>data</em>
followed by a newline.
Here <em>klen</em> is the number of bytes in <em>key</em>
and <em>dlen</em> is the number of bytes in <em>data</em>.
The end of all records is indicated by an extra newline.
For example, here are two records:</p>
<pre><code>+3,5:one->Hello
+3,7:two->Goodbye
</code></pre>
<p><em>key</em> and <em>data</em> may contain any characters,
including colons, dashes, newlines, and nulls.</p>
<p>Keys and data do not have to fit into memory,
but <code>cdbmake</code> needs roughly 16 bytes of memory per record.
A database cannot exceed 4 gigabytes (or 1 exabyte for <code>cdb64make</code>).</p>
<p><em>f</em> is portable across machines.</p>
<h3>SEE ALSO</h3>
<p><strong>cdbdump</strong>(1),
<strong>cdbget</strong>(1),
<strong>cdbmake-12</strong>(1),
<strong>cdbmake-sv</strong>(1),
<strong>cdbstats</strong>(1)</p><hr><font size=1><b>Version:</b>
This is version 2025.10.21 of the "cdbmake" web page.
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