apache/docs/manual/mod/mod_version.xml

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<modulesynopsis metafile="mod_version.xml.meta">
<name>mod_version</name>
<description>Version dependent configuration</description>
<status>Extension</status>
<sourcefile>mod_version.c</sourcefile>
<identifier>version_module</identifier>
<compatibility>Available in version 2.0.56 and later</compatibility>

<summary>
    <p>This module is designed for the use in test suites and large
    networks which have to deal with different httpd versions and
    different configurations. It provides a new container -- <directive
    type="section" module="mod_version">IfVersion</directive>, which
    allows a flexible version checking including numeric comparisons and
    regular expressions.</p>

    <example><title>Examples</title>
    <highlight language="config">
&lt;IfVersion 2.4.2&gt;
    # current httpd version is exactly 2.4.2
&lt;/IfVersion&gt;

&lt;IfVersion >= 2.5&gt;
    # use really new features :-)
&lt;/IfVersion&gt;
      </highlight>
    </example>

    <p>See below for further possibilities.</p>
</summary>

<directivesynopsis type="section">
<name>IfVersion</name>
<description>contains version dependent configuration</description>
<syntax>&lt;IfVersion [[!]<var>operator</var>] <var>version</var>&gt; ...
&lt;/IfVersion&gt;</syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context></contextlist>
<override>All</override>

<usage>
    <p>The <directive type="section">IfVersion</directive> section encloses
    configuration directives which are executed only if the
    <program>httpd</program> version
    matches the desired criteria. For normal (numeric) comparisons the
    <var>version</var> argument has the format
    <code><var>major</var>[.<var>minor</var>[.<var>patch</var>]]</code>, e.g.
    <code>2.1.0</code> or <code>2.2</code>. <var>minor</var> and
    <var>patch</var> are optional. If these numbers are omitted, they are
    assumed to be zero. The following numerical <var>operator</var>s are
    possible:</p>

    <table style="zebra" border="1">
    <tr><th><var>operator</var></th><th>description</th></tr>
    <tr><td><code>=</code> or <code>==</code></td>
        <td>httpd version is equal</td></tr>
    <tr><td><code>&gt;</code></td>
        <td>httpd version is greater than</td></tr>
    <tr><td><code>&gt;=</code></td>
        <td>httpd version is greater or equal</td></tr>
    <tr><td><code>&lt;</code></td>
        <td>httpd version is less than</td></tr>
    <tr><td><code>&lt;=</code></td>
        <td>httpd version is less or equal</td></tr>
    </table>

    <example><title>Example</title>
    <highlight language="config">
&lt;IfVersion >= 2.3&gt;
    # this happens only in versions greater or
    # equal 2.3.0.
&lt;/IfVersion&gt;
      </highlight>
    </example>

    <p>Besides the numerical comparison it is possible to match a
    <glossary ref="regex">regular expression</glossary>
    against the httpd version. There are two ways to write it:</p>

    <table style="zebra" border="1">
    <tr><th><var>operator</var></th><th>description</th></tr>
    <tr><td><code>=</code> or <code>==</code></td>
        <td><var>version</var> has the form
            <code>/<var>regex</var>/</code></td></tr>
    <tr><td><code>~</code></td>
        <td><var>version</var> has the form
            <code><var>regex</var></code></td></tr>
    </table>

    <example><title>Example</title>
    <highlight language="config">
&lt;IfVersion = /^2.4.[01234]$/&gt;
    # e.g. workaround for buggy versions
&lt;/IfVersion&gt;
      </highlight>
    </example>

    <p>In order to reverse the meaning, all operators can be preceded by an
    exclamation mark (<code>!</code>):</p>

    <highlight language="config">
&lt;IfVersion !~ ^2.4.[01234]$&gt;
    # not for those versions
&lt;/IfVersion&gt;
    </highlight>

    <p>If the <var>operator</var> is omitted, it is assumed to be
    <code>=</code>.</p>
</usage>
</directivesynopsis>

</modulesynopsis>