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

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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 immedi-
       ately.

       The  update  idletasks  command is useful in scripts where changes have
       been made to the	application's state and	you want those changes to  ap-
       pear  on	the display immediately, rather	than waiting for the script to
       complete.  Most display updates are performed as	idle callbacks,	so up-
       date  idletasks	will cause them	to run.	 However, there	are some kinds
       of updates that only happen in response to events, such as those	 trig-
       gered  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  occasion-
       ally 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(n), interp(n)

KEYWORDS
       asynchronous I/O, event,	flush, handler,	idle, update

Tcl				      7.5			     update(n)

NAME | SYNOPSIS | DESCRIPTION | EXAMPLE | SEE ALSO | KEYWORDS

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