1update(n)                    Tcl Built-In Commands                   update(n)
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NAME

8       update - Process pending events and idle callbacks
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SYNOPSIS

11       update ?idletasks?
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DESCRIPTION

15       This  command is used to bring the application “up to date” by entering
16       the event loop repeatedly until  all  pending  events  (including  idle
17       callbacks) have been processed.
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19       If  the  idletasks  keyword is specified as an argument to the command,
20       then no new events or errors are processed;  only  idle  callbacks  are
21       invoked.   This  causes  operations that are normally deferred, such as
22       display updates and window layout calculations, to be performed immedi‐
23       ately.
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25       The  update  idletasks  command is useful in scripts where changes have
26       been made to the application's state and  you  want  those  changes  to
27       appear  on  the display immediately, rather than waiting for the script
28       to complete.  Most display updates are performed as idle callbacks,  so
29       update idletasks will cause them to run.  However, there are some kinds
30       of updates that only happen in response to events, such as those  trig‐
31       gered  by  window  size changes; these updates will not occur in update
32       idletasks.
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34       The update command with no options is useful in scripts where  you  are
35       performing  a  long-running computation but you still want the applica‐
36       tion to respond to events such as user interactions;  if you  occasion‐
37       ally call update then user input will be processed during the next call
38       to update.
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EXAMPLE

41       Run computations for about a second and then finish:
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43              set x 1000
44              set done 0
45              after 1000 set done 1
46              while {!$done} {
47                  # A very silly example!
48                  set x [expr {log($x) ** 2.8}]
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50                  # Test to see if our time-limit has been hit.  This would
51                  # also give a chance for serving network sockets and, if
52                  # the Tk package is loaded, updating a user interface.
53                  update
54              }
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SEE ALSO

57       after(n), interp(n)
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KEYWORDS

60       asynchronous I/O, event, flush, handler, idle, update
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64Tcl                                   7.5                            update(n)