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.so man.macros

.TH vwait n 7.5 Tcl "Tcl Built-In Commands"

.BS

'\" Note:  do not modify the .SH NAME line immediately below!

.SH NAME

vwait \- Process events until a variable is written

.SH SYNOPSIS

\fBvwait\fR \fIvarName\fR

.BE

.SH DESCRIPTION

.PP

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

\fIvarName\fR.  Once \fIvarName\fR has been set, the \fBvwait\fR

command will return as soon as the event handler that modified

\fIvarName\fR completes.

.PP

In some cases the \fBvwait\fR command may not return immediately

after \fIvarName\fR is set.  This can happen if the event handler

that sets \fIvarName\fR does not complete immediately.  For example,

if an event handler sets \fIvarName\fR and then itself calls

\fBvwait\fR to wait for a different variable, then it may not return

for a long time.  During this time the top-level \fBvwait\fR is

blocked waiting for the event handler to complete, so it cannot

return either.

.SH KEYWORDS

event, variable, wait