Lua - Current time in milliseconds

Question

Is there a common way to get the current time in or with milliseconds?

There is os.time(), but it only provides full seconds.

Answer 1

Kevlar is correct.

An alternative to a custom DLL is Lua Alien

Answer 2

If you're using OpenResty then it provides for in-built millisecond time accuracy through the use of its ngx.now() function. Although if you want fine grained millisecond accuracy then you may need to call ngx.update_time() first. Or if you want to go one step further...

If you are using luajit enabled environment, such as OpenResty, then you can also use ffi to access C based time functions such as gettimeofday() e.g: (Note: The pcall check for the existence of struct timeval is only necessary if you're running it repeatedly e.g. via content_by_lua_file in OpenResty - without it you run into errors such as attempt to redefine 'timeval')

if pcall(ffi.typeof, "struct timeval") then
        -- check if already defined.
else
        -- undefined! let's define it!
        ffi.cdef[[
           typedef struct timeval {
                long tv_sec;
                long tv_usec;
           } timeval;

        int gettimeofday(struct timeval* t, void* tzp);
]]
end
local gettimeofday_struct = ffi.new("struct timeval")
local function gettimeofday()
        ffi.C.gettimeofday(gettimeofday_struct, nil)
        return tonumber(gettimeofday_struct.tv_sec) * 1000000 + tonumber(gettimeofday_struct.tv_usec)
end

Then the new lua gettimeofday() function can be called from lua to provide the clock time to microsecond level accuracy.

Indeed, one could take a similar approaching using clock_gettime() to obtain nanosecond accuracy.

Answer 3

If you're using lua with nginx/openresty you could use ngx.now() which returns a float with millisecond precision

Answer 4

Get current time in milliseconds.

os.time()

os.time()
return sec // only

posix.clock_gettime(clk)

https://luaposix.github.io/luaposix/modules/posix.time.html#clock_gettime

require'posix'.clock_gettime(0)
return sec, nsec

linux/time.h // man clock_gettime

/*
 * The IDs of the various system clocks (for POSIX.1b interval timers):
 */
#define CLOCK_REALTIME                  0
#define CLOCK_MONOTONIC                 1
#define CLOCK_PROCESS_CPUTIME_ID        2
#define CLOCK_THREAD_CPUTIME_ID         3
#define CLOCK_MONOTONIC_RAW             4
#define CLOCK_REALTIME_COARSE           5
#define CLOCK_MONOTONIC_COARSE          6

socket.gettime()

http://w3.impa.br/~diego/software/luasocket/socket.html#gettime

require'socket'.gettime()
return sec.xxx

as waqas says

---

compare & test

get_millisecond.lua

local posix=require'posix'
local socket=require'socket'

for i=1,3 do
    print( os.time() )
    print( posix.clock_gettime(0) )
    print( socket.gettime() )
    print''
    posix.nanosleep(0, 1) -- sec, nsec
end

output

lua get_millisecond.lua
1490186718
1490186718      268570540
1490186718.2686

1490186718
1490186718      268662191
1490186718.2687

1490186718
1490186718      268782765
1490186718.2688