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diff --git a/doc/expression.html b/doc/expression.html new file mode 100644 index 00000000..51d99900 --- /dev/null +++ b/doc/expression.html @@ -0,0 +1,24 @@ +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> +<html><head> +<meta http-equiv="Content-Language" content="en"><title>Expressions</title> + +</head> +<body> +<h1>Expressions</h1> +<p>Rsyslog supports expressions at a growing number of places. So +far, they are supported for filtering messages.</p> +<p></p> +<h2>Formal Definition</h2> + +<p>Below is the formal definition of expression format (in ABNF, RFC 2234):<br> +</p><pre>expr := e_and *("or" e_and)<br>e_and := e_cmp *("and" e_cmp)<br>e_cmp := val cmp_op val<br>val := ["+" / "-"] term *(("+" / "-") term)<br>term := factor *(("*" / "/" / "%") factor)<br>factor := ["not"] terminal<br>terminal := var / constant / function / "(" expr ")"<br>function := name "(" *("," expr) ")"<br>var := "$" varname<br>varname := msgvar / sysvar<br>msgvar := name<br>sysvar := "$" name<br>name := alpha *(alnum)<br>constant := string / number<br>string := simpstr / tplstr ; tplstr will be implemented in next phase<br>simpstr := "'" *char "'" ; use your imagination for char ;)<br>tplstr := '"' template '"' ; not initially implemented<br>number := 1*digit<br>cmp_op := "==" / "!=" / "<" / ">" / "<=" / ">=" <br>digit := %x30-39<br>alpha := "a" ... "z" # all letters<br>alnum :* alpha / digit / "_"<br></pre> +<p>[<a href="rsyslog_conf.html">rsyslog.conf overview</a>] +[<a href="manual.html">manual index</a>] [<a href="http://www.rsyslog.com/">rsyslog site</a>]</p> +<p><font size="2">This documentation is part of the +<a href="http://www.rsyslog.com/">rsyslog</a> +project.<br> +Copyright © 2008 by <a href="http://www.gerhards.net/rainer">Rainer +Gerhards</a> and +<a href="http://www.adiscon.com/">Adiscon</a>. +Released under the GNU GPL version 3 or higher.</font></p> +</body></html>
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