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'\" $Header: /cvsroot/aolserver/aolserver/doc/ns_filter.n,v 1.4 2003/04/10 22:01:14 shmooved Exp $
'\"
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.TH ns_filter 3aolserver 4.0 AOLserver "AOLserver Built-In Commands"
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
ns_register_filter, ns_register_proc, ns_register_trace \- Register a filter, proc or trace callback
.SH SYNOPSIS
\fBns_register_filter \fIoption \fR?\fIarg arg ...\fR?
.sp
\fBns_register_proc \fIoption \fR?\fIarg arg ...\fR?
.sp
\fBns_register_trace \fIoption \fR?\fIarg arg ...\fR?
.BE

.SH DESCRIPTION
.PP


.SS 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: 

.IP \fBTCL_OK\fR 12
(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.
.IP \fBTCL_BREAK\fR 12
(using: return "filter_break"): The server will not process any more pre-authorization filters for this connection, and it will continue on with authorization.
.IP \fBTCL_RETURN\fR 12
(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 functions 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.

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

.IP \fBTCL_OK\fR 12
(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.  
.IP \fBTCL_BREAK\fR 12
(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.  
.IP \fBTCL_RETURN\fR 12
(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.
.TP
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: 

.IP \fBTCL_OK\fR 12
(using: return "filter_ok"): The server will continue to the next trace filter.
.IP \fBTCL_BREAK\fR 12  
(using: return "filter_break"): The rest of the trace filters are ignored.
.IP \fBTCL_RETURN\fR 12
(using: return "filter_break"): The rest of the trace filters are ignored.
.PP

\fBSyntax for the registered procedure:\fR

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: 

.CS
.RE 
\fBns_register_filter\fR \fItrace\fR GET /noargs filter_noargs
\fBns_register_filter\fR \fItrace\fR GET /context filter_context fnord
\fBns_register_filter\fR \fItrace\fR 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
.CE

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 following 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: 

.CS
.RE
\fBns_register_filter\fR \fIpostauth\fR GET /threeargs threeargs aaa
\fBns_register_filter\fR \fIpostauth\fR GET /fourargs fourargs aaa bbb ccc

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

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

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". 

.SS ns_register_trace:
.IP "" 0
Register a Tcl trace script to a method and matching URL. 
(Note: This function is obsolete. Use \fBns_register_filter\fR instead.) 

\fBns_register_trace\fR 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 \fIURLpattern\fR, it calls the trace script with the connection id and any arguments (args) specified. 
The \fIURLpattern\fR can contain standard string-matching characters. For example, these are valid URLpatterns: 

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

Note
\fBns_register_trace\fR is similar to \fBns_register_proc\fR except that the pattern-matching for the URL is performed differently. With \fBns_register_proc\fR, 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 \fBns_register_trace\fR, the \fIURLpattern\fR is used to match URLs as a string with standard string-matching characters. 
\fBns_register_proc\fR results in a single match, whereas multiple ns_register_trace's can be matched and will be called. 


.SH "SEE ALSO"
ns_register_proc(n), ns_register_tag(n), ns_register_adptag(n)
.CE
.SH KEYWORDS