timeout using TCL

Question

Is there a way in TCL to enclose a piece of code in a timeout block? What I mean by that is that the block will exit after a particular timeout even if the execution is not complete. For instance:-

timeout (interval) {
#wait for socket connection here

}

If no connection is established in interval time, the block exits.

Thanks and Regards, Anjali

Answer 1

Anjali, You are looking for vwait.

Here is an example: 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!"
   }
}

Edit You will need to communicate with your UART device using non blocking I/O.