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<a name="3659">
<center><h1>4 Developing FastCGI <br>Applications in Tcl</h1></center>
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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's kit. <p>
</a><a name="4943">
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's kit for how to make your own FastCGI-savvy Tcl, if you need a version for some platform that we don't supply.<p>
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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>
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<h1> Getting Started</h1>
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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>
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Then, you have to divide FastCGI scripts into the following two sections:<p>
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<li>Initialization section, which is executed only once.
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<li>Response loop section, which gets executed every time the FastCGI script gets called.
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A response loop typically has the following format:<p>
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while {[FCGI_Accept] &gt;= 0 } {
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# body of response loop
</a>
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}
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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>
</a><a name="4853">
<h1> Example: TinyFastCGI</h1>
</a><a name="4343">
Here is a simple example of a FastCGI application written in Tcl:<p>
</a><pre><a name="4344">
#!fcgi-savvy-tcl

set count 0

# Response Loop
while {[FCGI_Accept] &gt;= 0 } {
        incr count
        puts -nonewline "Content-type: text/html\r\n\r\n"
        puts "&lt;title&gt;FastCGI Hello! (Tcl)&lt;/title&gt;"
        puts "&lt;h1&gt;FastCGI Hello! (Tcl)&lt;/h1&gt;"
        puts "Request number $count running on host 	&lt;i&gt;$env(SERVER_NAME)&lt;/i&gt;"
}
</pre>
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	4	<a href="cover.htm">[Top]</a> <a href="ch3perl.htm">[Prev]</a> <a href="apaman.htm">[Next]</a> <a href="ap_guida.htm">[Bottom]</a>
	5	<hr><br>
	6
	7	<a name="3659">
	8	<center><h1>4 Developing FastCGI <br>Applications in Tcl</h1></center>
	9	</a><a name="4835">
	10	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's kit. <p>
	11	</a><a name="4943">
	12	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's kit for how to make your own FastCGI-savvy Tcl, if you need a version for some platform that we don't supply.<p>
	13	</a><a name="4221">
	14	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>
	15	</a><a name="4222">
	16	<h1> Getting Started</h1>
	17	</a><a name="4223">
	18	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>
	19	</a><a name="4226">
	20	Then, you have to divide FastCGI scripts into the following two sections:<p>
	21	</a><ul><a name="4227">
	22	<li>Initialization section, which is executed only once.
	23	</a><a name="4228">
	24	<li>Response loop section, which gets executed every time the FastCGI script gets called.
	25	</a></ul><a name="4229">
	26	A response loop typically has the following format:<p>
	27	</a><pre><a name="4923">
	28	while {[FCGI_Accept] >= 0 } {
	29	</a>
	30	<a name="4925">
	31	# body of response loop
	32	</a>
	33	<a name="4367">
	34	}
	35	</a>
	36	</pre><a name="4233">
	37	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>
	38	</a><a name="4853">
	39	<h1> Example: TinyFastCGI</h1>
	40	</a><a name="4343">
	41	Here is a simple example of a FastCGI application written in Tcl:<p>
	42	</a><pre><a name="4344">
	43	#!fcgi-savvy-tcl
	44
	45	set count 0
	46
	47	# Response Loop
	48	while {[FCGI_Accept] >= 0 } {
	49	incr count
	50	puts -nonewline "Content-type: text/html\r\n\r\n"
	51	puts "<title>FastCGI Hello! (Tcl)</title>"
	52	puts "<h1>FastCGI Hello! (Tcl)</h1>"
	53	puts "Request number $count running on host <i>$env(SERVER_NAME)</i>"
	54	}
	55	</pre>
	56	<p>
	57	</a>
	58	<hr><br>
	59
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