update(3tcl)						       Tcl Built-In Commands						      update(3tcl)

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NAME

       update - Process pending events and idle callbacks

SYNOPSIS

       update ?idletasks?
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DESCRIPTION

       This  command  is used to bring the application "up to date" by entering the event loop repeatedly until all pending events (including idle
       callbacks) have been processed.

       If the idletasks keyword is specified as an argument to the command, then no new events or errors are processed;  only idle  callbacks  are
       invoked.   This causes operations that are normally deferred, such as display updates and window layout calculations, to be performed imme-
       diately.

       The update idletasks command is useful in scripts where changes have been made to the application's state and you  want	those  changes	to
       appear  on  the display immediately, rather than waiting for the script to complete.  Most display updates are performed as idle callbacks,
       so update idletasks will cause them to run.  However, there are some kinds of updates that only happen in response to events, such as those
       triggered by window size changes; these updates will not occur in update idletasks.

       The update command with no options is useful in scripts where you are performing a long-running computation but you still want the applica-
       tion to respond to events such as user interactions;  if you occasionally call update then user input will be  processed  during  the  next
       call to update.

EXAMPLE

       Run computations for about a second and then finish:
	      set x 1000
	      set done 0
	      after 1000 set done 1
	      while {!$done} {
		  # A very silly example!
		  set x [expr {log($x) ** 2.8}]

		  # Test to see if our time-limit has been hit.  This would
		  # also give a chance for serving network sockets and, if
		  # the Tk package is loaded, updating a user interface.
		  update
	      }

SEE ALSO

       after(3tcl), interp(3tcl)

KEYWORDS

       event, flush, handler, idle, update

Tcl									7.5							      update(3tcl)