vwait(n) [osx man page]

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

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NAME

       vwait - Process events until a variable is written

SYNOPSIS

       vwait varName
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DESCRIPTION

       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 varName has been set, the vwait command will return as soon as the event
       handler	that  modified varName completes.  varName must be 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 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
       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, otherwise 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

	      # 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(n), update(n)

KEYWORDS

       event, variable, wait

Tcl									8.0								  vwait(n)

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

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NAME

       set - Read and write variables

SYNOPSIS

       set varName ?value?
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DESCRIPTION

       Returns	the  value  of	variable  varName.   If value is specified, then set the value of varName to value, creating a new variable if one
       doesn't already exist, and return its value.  If varName contains an open parenthesis and ends with a close parenthesis, then it refers	to
       an  array  element:  the characters before the first open parenthesis are the name of the array, and the characters between the parentheses
       are the index within the array.	Otherwise varName refers to a scalar variable.	Normally, varName is unqualified  (does  not  include  the
       names of any containing namespaces), and the variable of that name in the current namespace is read or written.	If varName includes names-
       pace qualifiers (in the array name if it refers to an array element), the variable in the specified namespace is read or written.

       If no procedure is active, then varName refers to a namespace variable (global variable if the current namespace is the global  namespace).
       If  a  procedure  is active, then varName refers to a parameter or local variable of the procedure unless the global command was invoked to
       declare varName to be global, or unless a variable command was invoked to declare varName to be a namespace variable.

SEE ALSO

       expr(n), proc(n), trace(n), unset(n)

KEYWORDS

       read, write, variable

Tcl																	    set(n)

Linux and UNIX Man Pages

vwait(n) [osx man page]

Check Out this Related Man Page