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         FastCGI Programmer&#39;s Guide - Chapter 4, Developing FastCGI Applications in Tcl
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       <A NAME="3659"></A>
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         <H1>
            4 Developing FastCGI<BR>
            Applications in Tcl
         </H1>
      </DIV>
      <A NAME="4835"></A>
      <P>
         This chapter explains how to code FastCGI applications in Tcl. Prior to creating a FastCGI application, you
         must have a FastCGI-savvy version of the Tcl interpreter. Open Market develops Tcl binaries for popular
         platforms and makes them available with our developer&#39;s kit.
      </P>
      <P>
         <A NAME="4943"></A> The FastCGI-savvy binaries are extensions of standard Tcl, and are intended to replace
         your existing Tcl installation. There is no need to maintain two versions of Tcl: the version that we supply
         will work fine when invoked from a shell or a CGI program. There are also directions in the developer&#39;s
         kit for how to make your own FastCGI-savvy Tcl, if you need a version for some platform that we don&#39;t
         supply.
      </P>
      <P>
         <A NAME="4221"></A> In many cases, you can convert a Tcl script from CGI to FastCGI by adding a few lines of
         code to an existing script. For more complex scripts, you may also need to rearrange some existing code.
      </P>
      <BR>
      <BR>
      <H1>
         Getting Started
      </H1>
      <A NAME="4223"></A>
      <P>
         The first line of any Tcl script typically specifies the pathname of the Tcl interpreter itself. You must
         specify the pathname of a FastCGI-savvy Tcl.
      </P>
      <P>
         <A NAME="4226"></A> Then, you have to divide FastCGI scripts into the following two sections:
      </P>
      <BR>
      <BR>
      <UL>
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            <A NAME="4227"></A>
         </LI>
         <LI>
            Initialization section, which is executed only once. <A NAME="4228"></A>
         </LI>
         <LI>
            Response loop section, which gets executed every time the FastCGI script gets called.
         </LI>
      </UL>
      <A NAME="4229"></A>
      <P>
         A response loop typically has the following format:
      </P>
      <BR>
      <BR>
<PRE>
<A NAME="4923">while {[FCGI_Accept] &gt;= 0 } {
</A>
<A NAME="4925"># body of response loop
</A>
<A NAME="4367">}
</A>
</PRE>
      <A NAME="4233"></A>
      <P>
         The <CODE>FCGI_Accept</CODE> call returns 0 whenever a client requests the FastCGI script. Otherwise, the
         <CODE>FCGI_Accept</CODE> call returns -1.
      </P>
      <BR>
      <BR>
      <H1>
         Example: TinyFastCGI
      </H1>
      <A NAME="4343"></A>
      <P>
         Here is a simple example of a FastCGI application written in Tcl:
      </P>
      <BR>
      <BR>
<PRE>
<A NAME="4344"></A>
#!fcgi-savvy-tcl

set count 0

# Response Loop
while {[FCGI_Accept] &gt;= 0 } {
        incr count
        puts -nonewline &quot;Content-type: text/html\r\n\r\n&quot;
        puts &quot;&lt;title&gt;FastCGI Hello! (Tcl)&lt;/title&gt;&quot;
        puts &quot;&lt;h1&gt;FastCGI Hello! (Tcl)&lt;/h1&gt;&quot;
        puts &quot;Request number $count running on host  &lt;i&gt;$env(SERVER_NAME)&lt;/i&gt;&quot;
}
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