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<div class="section" id="vcl-syntax">
<h1>VCL Syntax<a class="headerlink" href="#vcl-syntax" title="Permalink to this headline">¶</a></h1>
<p>VCL has inherited a lot from C and it reads much like simple C or Perl.</p>
<p>Blocks are delimited by curly brackets, statements end with semicolons,
and comments may be written as in C, C++ or Perl according to your own
preferences.</p>
<p>Note that VCL doesn’t contain any loops or jump statements.</p>
<p>This section provides an outline of the more important parts of the
syntax. For a full documentation of VCL syntax please see
<a class="reference internal" href="../reference/vcl.html#vcl-7"><span class="std std-ref">VCL</span></a> in the reference.</p>
<div class="section" id="strings">
<h2>Strings<a class="headerlink" href="#strings" title="Permalink to this headline">¶</a></h2>
<p>Basic strings are enclosed in ” … “, and may not contain newlines.</p>
<p>Backslash is not special, so for instance in <cite>regsub()</cite> you do not need
to do the “count-the-backslashes” polka:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">regsub</span><span class="p">(</span><span class="s2">"barf"</span><span class="p">,</span> <span class="s2">"(b)(a)(r)(f)"</span><span class="p">,</span> <span class="s2">"</span><span class="se">\4\3\2</span><span class="s2">p"</span><span class="p">)</span> <span class="o">-></span> <span class="s2">"frap"</span>
</pre></div>
</div>
<p>Long strings are enclosed in {” … “}. They may contain any character
including “, newline and other control characters except for the NUL
(0x00) character. If you really want NUL characters in a string there
is a VMOD that makes it possible to create such strings.</p>
</div>
<div class="section" id="access-control-lists-acls">
<span id="vcl-syntax-acl"></span><h2>Access control lists (ACLs)<a class="headerlink" href="#access-control-lists-acls" title="Permalink to this headline">¶</a></h2>
<p>An ACL declaration creates and initializes a named access control list
which can later be used to match client addresses:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span>acl local {
"localhost"; // myself
"192.0.2.0"/24; // and everyone on the local network
! "192.0.2.23"; // except for the dialin router
}
</pre></div>
</div>
<p>If an ACL entry specifies a host name which Varnish is unable to
resolve, it will match any address it is compared to. Consequently,
if it is preceded by a negation mark, it will reject any address it is
compared to, which may not be what you intended. If the entry is
enclosed in parentheses, however, it will simply be ignored.</p>
<p>To match an IP address against an ACL, simply use the match operator:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="k">if</span> <span class="p">(</span><span class="n">client</span><span class="o">.</span><span class="n">ip</span> <span class="o">~</span> <span class="n">local</span><span class="p">)</span> <span class="p">{</span>
<span class="k">return</span> <span class="p">(</span><span class="n">pipe</span><span class="p">);</span>
<span class="p">}</span>
</pre></div>
</div>
</div>
<div class="section" id="operators">
<h2>Operators<a class="headerlink" href="#operators" title="Permalink to this headline">¶</a></h2>
<p>The following operators are available in VCL. See the examples further
down for, uhm, examples.</p>
<dl class="docutils">
<dt>=</dt>
<dd>Assignment operator.</dd>
</dl>
<dl class="docutils">
<dt>==</dt>
<dd>Comparison.</dd>
</dl>
<dl class="docutils">
<dt>~</dt>
<dd>Match. Can either be used with regular expressions or ACLs.</dd>
</dl>
<dl class="docutils">
<dt>!</dt>
<dd>Negation.</dd>
</dl>
<dl class="docutils">
<dt>&&</dt>
<dd>Logical <em>and</em></dd>
</dl>
<dl class="docutils">
<dt>||</dt>
<dd>Logical <em>or</em></dd>
</dl>
</div>
<div class="section" id="subroutines">
<h2>Subroutines<a class="headerlink" href="#subroutines" title="Permalink to this headline">¶</a></h2>
<p>A subroutine is used to group code for legibility or reusability:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">sub</span> <span class="n">pipe_if_local</span> <span class="p">{</span>
<span class="k">if</span> <span class="p">(</span><span class="n">client</span><span class="o">.</span><span class="n">ip</span> <span class="o">~</span> <span class="n">local</span><span class="p">)</span> <span class="p">{</span>
<span class="k">return</span> <span class="p">(</span><span class="n">pipe</span><span class="p">);</span>
<span class="p">}</span>
<span class="p">}</span>
</pre></div>
</div>
<p>Subroutines in VCL do not take arguments, nor do they return values.</p>
<p>To call a subroutine, use the call keyword followed by the subroutine’s name:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">call</span> <span class="n">pipe_if_local</span><span class="p">;</span>
</pre></div>
</div>
<p>Varnish has quite a few built in subroutines that are called for each
transaction as it flows through Varnish. These builtin subroutines are all
named <cite>vcl_*</cite>. Your own subroutines cannot start their name with <cite>vcl_</cite>.</p>
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<h3><a href="../index.html">Table Of Contents</a></h3>
<ul>
<li><a class="reference internal" href="#">VCL Syntax</a><ul>
<li><a class="reference internal" href="#strings">Strings</a></li>
<li><a class="reference internal" href="#access-control-lists-acls">Access control lists (ACLs)</a></li>
<li><a class="reference internal" href="#operators">Operators</a></li>
<li><a class="reference internal" href="#subroutines">Subroutines</a></li>
</ul>
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