Easiest way to make lua script wait/pause/sleep/block for a few seconds


I cant figure out how to get lua to do any common timing tricks, such as

  • sleep – stop all action on thread

  • pause/wait – don't go on to the next
    command, but allow other code in the
    application to continue

  • block – don't go on to next command until the
    current one returns

And I've read that a

while os.clock()<time_point do 

eats up CPU time.

Any suggestions? Is there an API call I'm missing?

UPDATE: I wrote this question a long time ago trying to get WOW Lua to replay actions on a schedule (i.e. stand, wait 1 sec, dance, wait 2 sec, sit. Without pauses, these happen almost all in the same quarter second.) As it turned out WOW had purposely disabled pretty much everything that allows doing action on a clock because it could break the game or enable bots. I figured to re-create a clock once it had been taken away, I'd have to do something crazy like create a work array (with an action and execution time) and then register an event handler on a bunch of common events, like mouse move, then in the even handler, process any action whose time had come. The event handler wouldn't actually happen every X milliseconds, but if it was happening every 2-100 ms, it would be close enough. Sadly I never tried it.

Best Solution

[I was going to post this as a comment on John Cromartie's post, but didn't realize you couldn't use formatting in a comment.]

I agree. Dropping it to a shell with os.execute() will definitely work but in general making shell calls is expensive. Wrapping some C code will be much quicker at run-time. In C/C++ on a Linux system, you could use:

static int lua_sleep(lua_State *L)
    int m = static_cast<int> (luaL_checknumber(L,1));
    usleep(m * 1000); 
    // usleep takes microseconds. This converts the parameter to milliseconds. 
    // Change this as necessary. 
    // Alternatively, use 'sleep()' to treat the parameter as whole seconds. 
    return 0;

Then, in main, do:

lua_pushcfunction(L, lua_sleep);
lua_setglobal(L, "sleep");

where "L" is your lua_State. Then, in your Lua script called from C/C++, you can use your function by calling:

sleep(1000) -- Sleeps for one second
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