vwait(n)                     Tcl Built-In Commands                    vwait(n)


       vwait - Process events until a variable is written

       vwait varName

       This  command enters the Tcl event loop to process events, blocking the
       application if no events are ready.   It  continues  processing  events
       until some event handler sets the value of variable varName.  Once var-
       Name has been set, the vwait command will return as soon as  the  event
       handler  that modified varName completes.  varName must globally scoped
       (either with a call to global for the varName, or with the full  names-
       pace path specification).

       In  some  cases the vwait command may not return immediately after var-
       Name is set.  This can happen if the event handler  that  sets  varName
       does  not  complete immediately.  For example, if an event handler sets
       varName and then itself calls vwait to wait for a  different  variable,
       then it may not return for a long time.  During this time the top-level
       vwait is blocked waiting for the event handler to complete, so it  can-
       not return either.


       event, variable, wait

Tcl                                   8.0                             vwait(n)