NAME

       ns_adp_abort, ns_adp_break, ns_adp_exception, ns_adp_return - ADP exception handling

SYNOPSIS

       ns_adp_abort ?result?
       ns_adp_break ?result?
       ns_adp_exception ?varName?
       ns_adp_return ?result?
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DESCRIPTION

       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 catch command to catch the exception and stop Tcl from returning control to ADP.
       The ns_adp_exception command can be used to test for this condition.

       ns_adp_abort ?result?
              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
              catch  command  in  script  block  which executes ns_adp_abort.  However, when that
              block returns control to the ADP execution engine, the stack will be continue to be
              unwound.   The  optional  result  argument, if present, will be used to set the Tcl
              interpreter result string.

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

       ns_adp_exception ?varName?
              This command returns a boolean value if an exception has been raised.  The optional
              varName provides the name of a variable to store one of ok, break, abort, or return
              to indicate the type of exception raised.

       ns_adp_return ?result?
              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
              return_value, if specified, becomes the return value of the ADP.   Note  that  this
              function  returns  only one level up the call stack.  By contrast, ns_adp_abort and
              ns_adp_break will return all the way up the call stack.  ns_adp_return 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 result  argument,  if  present,
              will be used to set the Tcl interpreter result string.

EXAMPLE

       The following example demonstrates halting execution of the ADP after returning a complete
       response with one of the ns_return style commands:

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

SEE ALSO

       ns_adp(n)

KEYWORDS

       ADP, dynamic pages, exception