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<!doctype html public "-//W30//DTD W3 HTML 2.0//EN">
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<!-- This file was generated using SDF 2.001 by
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<TITLE>SDF 2.001: SDF Reference: script Filter</TITLE>
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<H1>5.27. script Filter</H1>
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<H2><A NAME="Interface">Interface</A></H2>
<P>The general syntax is:</P>
<PRE>
!block <STRONG>script</STRONG>
...
!endblock
</PRE>
<P>See <A HREF="in_filif.html">Understanding Filter Interfaces</A>, if necessary.</P>
<HR>
<H2><A NAME="Description">Description</A></H2>
<P>The <EM>script</EM> filter can be used to embed arbitrary Perl source code within an SDF document. This is useful for many things including:</P>
<UL>
<LI>declaring Perl subroutines implementing SDF filters and macros
<LI>accessing databases
<LI>updating log files.</UL>
<HR>
<H2><A NAME="Examples">Examples</A></H2>
<PRE>
<B>!block</B> script
printf STDERR <TT>"Hello world!\n"</TT>;
<B>!endblock</B>
</PRE>
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<H2><A NAME="Limitations & Future Directions">Limitations & Future Directions</A></H2>
<P>As arbitrary sections of <A HREF="http://www.perl.com/perl/index.html">Perl</A> can be included and executed, the code can potentially cause harm. At the moment, the ability to update external files from within an SDF document is seen as a <EM>feature</EM>. However, a version of SDF which restricts the embedded Perl to "safe" operations would be nice.</P>
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