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<TITLE>Tcl Libraries -- When to Use Tcl Libraries</TITLE>
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<a name="15705">
</a><h3>When to Use Tcl Libraries</h3>
<p><a name="14320">
</a>The alternative to embedding Tcl scripts in HTML pages using ADPs (see <a href="tadp-ch.htm#2039">Chapter 2</a>), is to store Tcl scripts in Tcl libraries. The situations listed below are well-suited to the Tcl libraries approach.</p>
<ul><li><b>Inheritance:</b> If you want one Tcl script to handle an URL and all of its sub-URLs, it's better to store the script in a Tcl library and register it using <b>ns_register_proc</b> to handle an URL hierarchy. For example, you may want to manage a server domain name change by redirecting every response to the corresponding domain name on another server.<a name="14324">
</a>
<p><li><b>Special Extensions:</b> If you want one Tcl script to handle all files with a specific extension, like /*.csv, you would register the script with <b>ns_register_proc</b> to handle those files.<a name="14325">
</a>
<p><li><b>Scheduled Procedures:</b> If you want a Tcl script to be run at specific intervals, you can use the <b>ns_schedule_*</b> functions to run a script from the Tcl library at scheduled intervals. These procedures do not normally involve returning HTML pages and so are not well suited to ADPs.<a name="14326">
</a>
<p><li><b>Filters:</b> If you want a Tcl script to be called at pre-authorization, post-authorization, or trace time for a group of URLs, you would register a filter using the <b>ns_register_filter</b> function.<a name="14327">
</a>
<p><li><b>Re-using Tcl Scripts:</b> If there are Tcl scripts that you want to use in multiple situations, you can store them in a Tcl library and invoke them from within any ADP or Tcl script.<a name="14328">
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