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+++ b/relpipe-data/examples-awk-through-xml.xml	Sat Dec 28 16:19:41 2019 +0100
@@ -0,0 +1,55 @@
+<stránka
+	xmlns="https://trac.frantovo.cz/xml-web-generator/wiki/xmlns/strana"
+	xmlns:m="https://trac.frantovo.cz/xml-web-generator/wiki/xmlns/makro">
+	
+	<nadpis>AWKing through a XML file</nadpis>
+	<perex>use AWK to filter data from a D-Bus policy file</perex>
+	<m:pořadí-příkladu>03700</m:pořadí-příkladu>
+
+	<text xmlns="http://www.w3.org/1999/xhtml">
+		
+		<p>
+			The <a href="https://en.wikipedia.org/wiki/AWK">AWK</a> programming language and tool is designed for processing text
+			but in <m:name/> we can use all the power of AWK for processing relational data that came from various sources.
+			And „all the power“ means that we internally call the regular AWK implementation installed in our system (which is usually GNU AWK).
+		</p>
+		
+		<p>
+			In this example, we will read a D-Bus policy configuration file (an XML)
+			and filter it using a simple AWK expression.
+			The XML file looks like this:
+		</p>
+		
+		<m:pre jazyk="xml" src="examples/awk-through-xml.xml"/>
+		
+		<p>
+			We separate particular steps of our pipeline to shell functions for better readability and maintenance:
+		</p>
+	
+		<m:pre jazyk="bash" src="examples/awk-through-xml.sh"/>
+		
+		<p>
+			This simple sequence of steps will generate following result:
+		</p>
+		
+		<m:pre jazyk="text" src="examples/awk-through-xml.txt"/>
+		
+		<p>
+			We have processed two relations.
+			One (<code>limit</code>) was just passed through
+			while another (<code>policy</code>) was transformed.
+			In this case, we did just restriction (filtered certain records), but we can do also projections or other relational operations in our pipelines.
+		</p>
+		
+		<p>
+			This example also shows how we can structure our scripts – compose the pipeline from reusable fragments (shell functions).
+			Once we write the <em>parse</em> function for an input format, we can use it many times, with various filters/transformations and output formatters.
+		</p>
+		<p>
+			Instead of converting to an output format, we can also <m:a href="examples-out-bash">execute arbitrary system commands</m:a> for each record 
+			(while having particular attribute values reliably separated in shell variables).
+		</p>
+		
+	</text>
+
+</stránka>