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Tcl_BackgroundError(3)      Tcl Library Procedures      Tcl_BackgroundError(3)




NAME

       Tcl_BackgroundError - report Tcl error that occurred in background pro-
       cessing


SYNOPSIS

       #include <tcl.h>

       Tcl_BackgroundError(interp)


ARGUMENTS

       Interpreter in which the error occurred.



DESCRIPTION

       This procedure is typically invoked when a Tcl error occurs during such
       as  executing  an  event handler.  When such an error occurs, the error
       condition is reported to Tcl or to a widget or some other C  code,  and
       there  is not usually any obvious way for that code to report the error
       to the user.  In these cases the code calls Tcl_BackgroundError with an
       interp   argument  identifying  the  interpreter  in  which  the  error
       occurred.  At the  time  Tcl_BackgroundError  is  invoked,  the  inter-
       preter's  result  is  expected  to contain an error message.  Tcl_Back-
       groundError will invoke the command registered in that  interpreter  to
       handle background errors by the interp bgerror command.  The registered
       handler command is meant to report the error in an application-specific
       fashion.  The handler command receives two arguments, the result of the
       interp, and the return options of the interp  at  the  time  the  error
       occurred.  If the application registers no handler command, the default
       handler command will attempt to call bgerror to report the  error.   If
       an  error  condition  arises  while  invoking the handler command, then
       Tcl_BackgroundError reports the error itself by printing a  message  on
       the standard error file.

       Tcl_BackgroundError  does  not  invoke  the handler command immediately
       because this could potentially  interfere  with  scripts  that  are  in
       process  at  the time the error occurred.  Instead, it invokes the han-
       dler command later as an idle callback.

       It is possible for many background errors to accumulate before the han-
       dler command is invoked.  When this happens, each of the errors is pro-
       cessed in order.  However, if the handle command returns a break excep-
       tion, then all remaining error reports for the interpreter are skipped.



KEYWORDS

       background, bgerror, error, interp



Tcl                                   7.5               Tcl_BackgroundError(3)

BackgdErr 8.5.4 - Generated Sun Aug 17 16:14:48 CDT 2008
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