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'\" $Header: /cvsroot/aolserver/aolserver/doc/ns_adp_exception.n,v 1.1 2006/04/13 19:07:12 jgdavidson Exp $
'\"
'\" 
'\" The definitions below are for supplemental macros used in Tcl/Tk
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..
.TH ns_adp_exception 3aolserver 4.5 AOLserver "AOLserver Built-In Commands"
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
ns_adp_abort, ns_adp_break, ns_adp_exception, ns_adp_return \- ADP exception handling
.SH SYNOPSIS
.nf
\fBns_adp_abort\fR ?\fIresult\fR?
\fBns_adp_break\fR ?\fIresult\fR?
\fBns_adp_exception\fR ?\fIvarName\fR?
\fBns_adp_return\fR ?\fIresult\fR?
.fi
.BE

.SH DESCRIPTION
.PP
These commands enable early return and interrupt of an ADP execution.
Internally, the exception routines sets a flag and return TCL_ERROR
to begin unwinding the current Tcl call stack and return control
to the ADP evaluation engine.  It is possible for an enclosing
\fBcatch\fR command to catch the exception and stop Tcl from returning
control to ADP.  The \fBns_adp_exception\fR command can be used to
test for this condition.

.TP
\fBns_adp_abort\fR ?\fIresult\fR?
This command stops ADP processing, raising an execution and unwinding
the stack to the top level as an error condition.  The request
handling code which invokes the first ADP file will normallly
generate an error message in this case, ignoring the contents of
the output buffer, if any.  Note that the exeception can be caught
by a \fBcatch\fR command in script block which executes \fBns_adp_abort\fR.
However, when that block returns control to the ADP execution engine,
the stack will be continue to be unwound.  The optional \fIresult\fR
argument, if present, will be used to set the Tcl interpreter result
string.

.TP
\fBns_adp_break\fR ?\fIresult\fR?
This command stops execution of ADP and unwinds the ADP call stack.
Unlike \fBns_adp_abort\fR, the request handling code will generate
a normal HTTP response with any contents of the output buffer.  The
optional \fIresult\fR argument, if present, will be used to set the
Tcl interpreter result string.

.TP
\fBns_adp_exception\fR ?\fIvarName\fR?
This command returns a boolean value if an exception has been raised.
The optional \fIvarName\fR provides the name of a variable to store
one of \fIok\fR, \fIbreak\fR, \fIabort\fR, or \fIreturn\fR to
indicate the type of exception raised.

.TP
\fBns_adp_return\fR ?\fIresult\fR?
This function halts processing of the current ADP and sends any
pending output (from ns_adp_puts or static HTML) up to the point
where it was called to the browser. Nothing in the current ADP is
output or executed after it is called.  The \fIreturn_value\fR, if
specified, becomes the return value of the ADP.  Note that this
function returns only one level up the call stack.  By contrast,
\fBns_adp_abort\fR and \fBns_adp_break\fR will return all the way
up the call stack.  \fBns_adp_return\fR is typically used from an
ADP included by another ADP, to stop processing of the inner ADP
while allowing the calling ADP to continue.  The optional \fIresult\fR
argument, if present, will be used to set the Tcl interpreter result
string.

.SH EXAMPLE
The following example demonstrates halting execution of the ADP
after returning a complete response with one of the \fBns_return\fR
style commands:

.CS
<%
if !$authorized {
	ns_returnunauthorized; # Send complete response.
	ns_adp_abort; # Execution stops here.
}
%>.
.CE

.SH "SEE ALSO"
ns_adp(n)

.SH KEYWORDS
ADP, dynamic pages, exception