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

Question

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   lt time point do  --nothing end   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

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I believe for windows you may use  os execute  ping 1 1 1 1  n 1  w  lt time in milliseconds gt   gt nul as a simple timer   remove the   lt    when inserting the time in milliseconds   there is a space between the rest of the code and  gt nul

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It doesn t get easier than this  Sleep might be implemented in your FLTK or whatever  but this covers all the best ways to do standard sort of system sleeps without special event interrupts  Behold   -- we  pcall   try catch  the  ex   which had better include os sleep -- it may be a part of the standard library in future Lua versions  past 5 2  local ok ex   pcall require  ex   if ok then    -- print  Ex      -- we need a hack now too  ex install    you say  okay    pcall ex install     -- let s try something else  why not     if ex sleep and not os sleep then os sleep   ex sleep end end  if not os sleep then    -- we make os sleep    -- first by trying ffi  which is part of LuaJIT  which lets us write C code    local ok ffi   pcall require  ffi      if ok then       -- print  FFI         -- we can use FFI       -- let s just check one more time to make sure we still don t have os sleep       if not os sleep then          -- okay  here is our custom C sleep code           ffi cdef               void Sleep int ms               int poll struct pollfd  fds unsigned long nfds int timeout                        if ffi os     Windows  then             os sleep   function sec                 ffi C Sleep sec 1000              end          else             os sleep   function sec                 ffi C poll nil 0 sec 1000              end          end       end    else       -- if we can t use FFI  we try LuaSocket  which is just called  socket        -- I m 99 99999999  sure of that       local ok socket   pcall require  socket         --    but I m not 100  sure of that       if not ok then local ok socket   pcall require  luasocket   end       -- so if we re really using socket          if ok then          -- print  Socket            -- we might as well confirm there still is no os sleep          if not os sleep then             -- our custom socket select to os sleep code              os sleep   function sec                 socket select nil nil sec              end          end       else          -- now we re going to test  alien           local ok alien   pcall require  alien            if ok then          -- print  Alien            -- beam me up                if not os sleep then                -- if we still don t have os sleep  that is                -- now  I don t know what the hell the following code does                if alien platform     windows  then                   kernel32   alien load  kernel32 dll                     local slep   kernel32 Sleep                   slep types ret  void  abi  stdcall   uint                     os sleep   function sec                       slep sec 1000                    end                else                   local pol   alien default poll                   pol types  struct    unsigned long    int                     os sleep   function sec                       pol nil 0 sec 1000                    end                end             end          elseif package config match        then             -- print  busywait               -- if the computer is politically opposed to NIXon  we do the busywait             -- and shake it all about             os sleep   function sec                 local timr   os time                  repeat until os time    gt  timr   sec             end          else             -- print  NIX               -- or we get NIXed             os sleep   function sec                 os execute  sleep      sec              end          end       end    end end

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cy   function       local T   os time           coroutine yield coroutine resume coroutine create function       end        return os time  -T end sleep   function time      if not time or time    0 then          time   cy       end     local t   0     repeat         local T   os time           coroutine yield coroutine resume coroutine create function   end            t   t    os time  -T      until t  gt   time end

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You can t do it in pure Lua without eating CPU  but there s a simple  non-portable way   os execute  sleep 1     it will block   Obviously  this only works on operating systems for which  sleep 1  is a valid command  for instance Unix  but not Windows

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This should work       os execute  PAUSE

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It s also easy to use Alien as a libc msvcrt wrapper    gt  luarocks install alien   Then from lua   require  alien   if alien platform     windows  then     -- untested       libc   alien load  msvcrt dll   else     libc   alien default end   usleep   libc usleep usleep types  int    uint    function sleep ms      while ms  gt  1000 do         usleep 1000          ms   ms - 1000     end     usleep 1000   ms  end  print  hello   sleep 500   -- sleep 500 ms print  world     Caveat lector  I haven t tried this on MSWindows  I don t even know if msvcrt has a usleep

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I agree with John on wrapping the sleep function  You could also use this wrapped sleep function to implement a pause function in lua  which would simply sleep then check to see if a certain condition has changed every so often   An alternative is to use hooks    I m not exactly sure what you mean with your third bulletpoint  don t commands usually complete before the next is executed   but hooks may be able to help with this also   See  Question  How can I end a Lua thread cleanly  for an example of using hooks

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You want  nbsp win Sleep milliseconds   methinks   Yeah  you definitely don t want to do a busy-wait like you describe

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Pure Lua uses only what is in ANSI standard C   Luiz Figuereido s lposix module contains much of what you need to do more systemsy things

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for windows you can do this   os execute  CHOICE  n  d y  c yn  t 5

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You can do this   function Sleep seconds      local endTime   os time     seconds     while os time    lt  endTime do     end end print  This is printed first    Sleep 5  print  This is printed 5 seconds later

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You can use   os execute  sleep 1   -- I think you can do every command of CMD using os execute  command     or you can use   function wait waitTime      timer   os time       repeat until os time    gt  timer   waitTime end  wait YourNumberHere

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Sleep Function - Usage   sleep 1  -- sleeps for 1 second  local clock   os clock function sleep n   -- seconds    local t0   clock      while clock   - t0  lt   n do    end end   Pause Function - Usage   pause   -- pause and waits for the Return key  function pause      io stdin read  l  end   hope  this is what you needed   D - Joe DF

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For the second request  pause wait  where you stop processing in Lua and continue to run your application  you need coroutines   You end up with some C code like this following   Lthread lua newthread L   luaL loadfile Lthread  file   while   status lua resume Lthread  0     LUA YIELD         do some C code here        and in Lua  you have the following   function try pause  func  param    local rc func param    while rc    false do     coroutine yield       rc func param    end end  function is data ready  data    local rc true   -- check if data is ready  update rc to false if not ready   return rc end  try pause is data ready  data

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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 lt int gt   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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require  alien   if alien platform     windows  then   kernel32   alien load  kernel32 dll     sleep   kernel32 Sleep   sleep types ret  void  abi  stdcall   uint   else   -- untested       libc   alien default   local usleep   libc usleep   usleep types  int    uint     sleep   function ms      while ms  gt  1000 do       usleep 1000        ms   ms - 1000     end     usleep 1000   ms    end end   print  hello   sleep 500   -- sleep 500 ms print  world

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I would implement a simple function to wrap the host system s sleep function in C

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If you happen to use LuaSocket in your project  or just have it installed and don t mind to use it  you can use the socket sleep time  function which sleeps for a given amount of time  in seconds    This works both on Windows and Unix  and you do not have to compile additional modules   I should add that the function supports fractional seconds as a parameter  i e  socket sleep 0 5  will sleep half a second  It uses Sleep   on Windows and nanosleep   elsewhere  so you may have issues with Windows accuracy when time gets too low

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I started with Lua but  then I found that I wanted to see the results instead of just the good old command line flash  So i just added the following line to my file and hey presto  the standard   please press any key to continue     os execute  PAUSE     My example file is only a print and then a pause statment so I am sure you don t need that posted here   I am not sure of the CPU implications of a running a process for a full script   However stopping the code mid flow in debugging could be useful

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

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