## THREADKILL Halt execution of a thread

Section: FreeMat Threads

### Usage

The `threadkill` function stops (or attempts to stop) execution of the given thread. It works only for functions defined in M-files (i.e., not for built in or imported functions), and it works by setting a flag that causes the thread to stop execution at the next available statement. The syntax for this function is

      threadkill(handle)

where `handle` is the value returned by a `threadnew` call. Note that the `threadkill` function returns immediately. It is still your responsibility to call `threadfree` to free the thread you have halted. You cannot kill the main thread (thread id `1`).

### Example

Here is an example of stopping a runaway thread using `threadkill`. Note that the thread function in this case is an M-file function. We start by setting up a free running counter, where we can access the counter from the global variables.

         freecount.m
    function freecount
      global count
      if (~exist('count')) count = 0; end  % Initialize the counter
      while (1)
        count = count + 1;                 % Update the counter
      end

We now launch this function in a thread, and use `threadkill` to stop it:

    --> a = threadnew;
    --> global count                   % register the global variable count
    --> count = 0;
    --> threadstart(a,'freecount',0)   % start the thread
    --> count                          % it is counting

    ans =
     7145

    --> sleep(1)                       % Wait a bit
    --> count                          % it is still counting

    ans =
     485030

    --> threadkill(a)                  % kill the counter
    --> threadwait(a,1000)             % wait for it to finish

    ans =
     1

    --> count                          % The count will no longer increase

    ans =
     485031

    --> sleep(1)
    --> count

    ans =
     485031

    --> threadfree(a)