LUA Sleep Function

最新推荐文章于 2024-01-19 09:42:59 发布

转载最新推荐文章于 2024-01-19 09:42:59 发布 · 4.2k 阅读

文章标签：

#function #lua #windows #library #vb #extension

lua 专栏收录该内容

19 篇文章

订阅专栏

本文介绍了在Lua中实现程序暂停功能的各种解决方案，包括使用忙等待、C扩展、外部命令如sleep、利用I/O等待、调用WScript以及使用select()函数等方法。这些方案覆盖了不同场景和平台的需求。

转自:http://lua-users.org/wiki/SleepFunction

A common need is to pause (sleep) a program for a certain number of seconds, preferably without busy waiting.

This function to do this without busy waiting does not exist in ANSI C, so it does not exist in stock Lua. However, there are extension libraries and calls to external programs that can do this.

Solution: Busy Wait

local clock = os.clock
function sleep(n)  -- seconds
  local t0 = clock()
  while clock() - t0 <= n do end
end
-- warning: clock can eventually wrap around for sufficiently large n
-- (whose value is platform dependent).  Even for n == 1, clock() - t0
-- might become negative on the second that clock wraps.

Solution: C extension

There is a sleep function in ExtensionProposal. This may call Win32 Sleep or POSIX usleep.

The lalarm library[1] can set an alarm on POSIX.

If an FFI interface (Alien or c/invoke -- BindingCodeToLua) is available, you can call whichever OS function you have.

Solution: sleep command

function sleep(n)
  os.execute("sleep " .. tonumber(n))
end

Windows does not have such a built-in command. However, there's a sleep in the Windows Server Resource Kit. There is also sleep in Cygwin and MinGW.

Solution: ping or other programs

function sleep(n)
  os.execute("ping -n " .. tonumber(n) .. " localhost > NUL")
end

This is mainly for Windows in the absence of a sleep command. Other variations exist, e.g. "perl -e 'sleep(" .. tonumber(n) .. ")'".

Solution: I/O wait

io.stdin:read'*l'

This is not a sleep but may be useful in similar cases. It waits for the use to press the Enter key.

Solution: Using WScript (Windows)

function sleep(n)
  local vb = "test.vbs"
  local f = assert(io.open(vb,"w"))
  f:write("WScript.Sleep(" .. (tonumber(n) * 1000) .. ")/n")
  f:close()
  os.execute(vb)
end

See [2].

Solution: select()

The select() timeout provides a fairly portable sub-second sleep, if you can tolerate the socket library dependency.

require "socket"

function sleep(sec)
    socket.select(nil, nil, sec)
end

sleep(0.2)