Manual Pages for UNIX Operating System command usage for man vwait

Tcl Built-In Commands                                   vwait(1T)



_________________________________________________________________

NAME
     vwait - Process events until a variable is written

SYNOPSIS
     vwait varName
_________________________________________________________________


DESCRIPTION
     This command enters the Tcl event loop  to  process  events,
     blocking the application if no events are ready.  It contin-
     ues processing events until  some  event  handler  sets  the
     value  of  variable varName.  Once varName 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 namespace path specification).

     In some cases the vwait command may not  return  immediately
     after  varName is set.  This can happen if the event handler
     that sets varName does not complete immediately.  For  exam-
     ple,  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 cannot return either.

EXAMPLES
     Run the event-loop continually until some event calls  exit.
     (You  can  use any variable not mentioned elsewhere, but the
     name forever reminds you at a glance of the intent.)
          vwait forever

     Wait five seconds for a connection to a server socket,  oth-
     erwise close the socket and continue running the script:
          # Initialise the state
          after 5000 set state timeout
          set server [socket -server accept 12345]
          proc accept {args} {
             global state connectionInfo
             set state accepted
             set connectionInfo $args
          }

          # Wait for something to happen
          vwait state

          # Clean up events that could have happened
          close $server
          after cancel set state timeout



Tcl                     Last change: 8.0                        1






Tcl Built-In Commands                                   vwait(1T)



          # Do something based on how the vwait finished...
          switch $state {
             timeout {
                puts "no connection on port 12345"
             }
             accepted {
                puts "connection: $connectionInfo"
                puts [lindex $connectionInfo 0] "Hello there!"
             }
          }


SEE ALSO
     global(1T), update(1T)


KEYWORDS
     event, variable, wait

ATTRIBUTES
     See attributes(5) for descriptions of the  following  attri-
     butes:

     _______________________________________
    |   ATTRIBUTE TYPE   |  ATTRIBUTE VALUE|
    |____________________|__________________|_
    | Availability       |  runtime/tcl-8  |
    |____________________|__________________|_
    | Interface Stability|  Uncommitted    |
    |____________________|_________________|

NOTES
     Source for Tcl is available on http://opensolaris.org.






















Tcl                     Last change: 8.0                        2