ns_filter(3aolserver)					    AOLserver Built-In Commands 				     ns_filter(3aolserver)

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NAME

       ns_register_filter, ns_register_proc, ns_register_trace - Register a filter, proc or trace callback

SYNOPSIS

       ns_register_filter option ?arg arg ...?

       ns_register_proc option ?arg arg ...?

       ns_register_trace option ?arg arg ...?
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DESCRIPTION

   ns_register_filter:
       Registers  a  Tcl  filter  script  for the specified method/URL combination on a virtual server. The script can be called at one or more of
       three given times: pre-authorization, post-authorization before page data has been returned to the user, and after the connection has  been
       processed and closed.

       This  function  will  be called at the specified stage of a connection, if the method/URL combination for the filter matches the method/URL
       combination for the connection using glob style matching.

       The URLpattern can contain standard string-matching characters. For example, these are valid URL patterns:

       /employees/*.tcl /accounts/*/out

       Valid values for the "when" argument are: preauth, postauth, and trace.	Using pre-authorization, the procedure will  be  called  (assuming
       that the method/URL combination matches) just before authorization. If the procedure returns with a code of:

       TCL_OK	   (using:  return  "filter_ok"):  The server will continue to the next pre-authorization filter for this connection, or, if there
		   are no more pre-authorization filters, it will continue on with authorization.

       TCL_BREAK   (using: return "filter_break"): The server will not process any more pre-authorization filters for this connection, and it will
		   continue on with authorization.

       TCL_RETURN  (using:  return  "filter_return"): The server will close the connection and will not run any more pre-authorization filters. It
		   will not authorize the request, and it will not run the function registered for this METHOD/URL. It WILL run  any  trace  func-
		   tions  registered  for  this  METHOD/URL,  usually  including logging. It is assumed that the filter has sent a proper response
		   (e.g., using ns_return) to the client before returning TCL_RETURN.

       Using post-authorization, the procedure will be called (assuming that the method/URL combination matches) just after successful	authoriza-
       tion. If the procedure returns:

       TCL_OK	   (using:  return  "filter_ok"): The server will continue to the next post-authorization filter for this connection, or, if there
		   are no more post-authorization filters, it will run the function registered to handle this request.

       TCL_BREAK   (using: return "filter_break"): The server will not process any more post-authorization filters for	this  connection,  and	it
		   will run the function registered to handle this request.

       TCL_RETURN  (using:  return "filter_return"): The server will close the connection and will not run any more post-authorization filters and
		   it will not run the function registered for this METHOD/URL. It WILL run any trace functions registered  for  this  METHOD/URL,
		   usually  including  logging. It is assumed that the filter has returned a proper response (e.g., using ns_return) to the client
		   before returning TCL_RETURN.

       Using trace, the procedure will be called (assuming that the method/URL combination match) after the connection has been totally  processed
       and closed. If the procedure returns:

       TCL_OK	   (using: return "filter_ok"): The server will continue to the next trace filter.

       TCL_BREAK   (using: return "filter_break"): The rest of the trace filters are ignored.

       TCL_RETURN  (using: return "filter_break"): The rest of the trace filters are ignored.

       Syntax for the registered procedure:

       The conn (connection) argument is optional for procedures registered by ns_register_filter if the procedure has 1 or 2 arguments (including
       why but not including conn). The following examples show the variations that can be used in this case:

       ns_register_filter trace GET /noargs filter_noargs
       ns_register_filter trace GET /context filter_context fnord
       ns_register_filter trace GET /conncontext filter_conncontext

       proc filter_noargs { why } {
	   ns_log Notice "filter noargs"
	   return filter_ok
       } ;# filter_noargs

       proc filter_context { arg why } {
	   ns_log Notice "filter context. Arg: $arg"
	   return filter_ok
       } ;# filter_noargs

       proc filter_conncontext { conn arg why } {
	   ns_log Notice "filter conn context"
	   return filter_ok
       } ;# filter_noargs

       The conn (connection) argument is required for procedures registered by ns_register_filter  if  the  procedure  has  3  or  more  arguments
       (including  why but not including conn). The conn argument is automatically filled with the connection information. The first argument fol-
       lowing conn will always take the value supplied by ns_register_filter, if there is one, or an empty value. The why argument at the  end	is
       automatically  filled  with  the type of filter requested. All other arguments must supply a default value. The following examples show the
       variations that can be used in this case:

       ns_register_filter postauth GET /threeargs threeargs aaa
       ns_register_filter postauth GET /fourargs fourargs aaa bbb ccc

       proc threeargs { conn context { greeble bork } why } {
	   ...
       } ;

       proc fourargs { conn context { greeble bork } {hoover quark} why } {
	  ...
       } ;

       When a GET of /threeargs is requested, the conn and why arguments will be filled automatically, the context argument will be assigned "aaa"
       and  the greeble argument will be assigned the default value "bork".  When a GET of /fourargs is requested, the conn and why arguments will
       be filled automatically, the context argument will be assigned "aaa", the greeble argument will be assigned "bbb", and the hoover  argument
       will be assigned the default value "quark".

   ns_register_trace:

       Register a Tcl trace script to a method and matching URL.  (Note: This function is obsolete. Use ns_register_filter instead.)

       ns_register_trace  registers a Tcl script as a trace for the specified method/URL combination. After the server handles the request for the
       specified method on an URL that matches the URLpattern, it calls the trace script with the connection id and any  arguments  (args)  speci-
       fied.  The URLpattern can contain standard string-matching characters. For example, these are valid URLpatterns:

       /employees/*.tcl /accounts/*/out

       Note ns_register_trace is similar to ns_register_proc except that the pattern-matching for the URL is performed differently. With ns_regis-
       ter_proc, the specified URL is used to match that URL and any URL below it in the hierarchy. Wildcards such as "*" are meaningful only  for
       the  final  part of the URL, such as /scripts/*.tcl. With ns_register_trace, the URLpattern is used to match URLs as a string with standard
       string-matching characters.  ns_register_proc results in a single match, whereas multiple ns_register_trace's can be matched  and  will	be
       called.

SEE ALSO

       ns_register_proc(n), ns_register_tag(n), ns_register_adptag(n)

KEYWORDS

AOLserver								4.0						     ns_filter(3aolserver)