How do I get elapsed time in milliseconds in Ruby

Question

If I have a Time object got from    Time now   and later I instantiate another object with that same line  how can I see how many milliseconds have passed  The second object may be created that same minute  over the next minutes or even hours

User · Answer

L gives milliseconds in ruby  require  time  puts Time now strftime   Y- m- dT H  M  S  L     or  puts Time now strftime   Y- m- d  H  M  S  L     will give you current timestamp in milliseconds

User · Answer

The answer is something like   t start   Time now   time-consuming operation t end   Time now  milliseconds    t start - t end    1000 0   However  the Time now approach risks to be inaccurate  I found this post by Luca Guidi   https   blog dnsimple com 2018 03 elapsed-time-with-ruby-the-right-way      system clock is constantly floating and it doesn t move only forwards  If your calculation of elapsed time is based on it  you re very likely to run into calculation errors or even outages    So  it is recommended to use Process clock gettime instead  Something like   def measure time   start time   Process clock gettime Process  CLOCK MONOTONIC    yield   end time   Process clock gettime Process  CLOCK MONOTONIC    elapsed time   end time - start time   elapsed time round 3  end   Example   elapsed   measure time do       your time-consuming task here      sleep 2 2321 end    gt  2 232

User · Answer

I think the answer is incorrectly chosen  that method gives seconds  not milliseconds   t   Time now t  o f   gt  1382471965 146   Here I suppose the floating value are the milliseconds

User · Answer

To get time in milliseconds  it s better to add  round 3   so it will be more accurate in some cases   puts Time now to f     gt  1453402722 577573   Time now to f round 3  1000  to i      gt  1453402722578

User · Answer

Try subtracting the first Time now from the second  Like so   a   Time now sleep 3  puts Time now - a   about 3 0   This gives you a floating-point number of the seconds between the two times  and with that  the milliseconds

User · Answer

Time now to f can help you but it returns seconds   In general  when working with benchmarks I    put in variable the current time  insert the block to test  put in a variable the current time  subtracting the preceding current-time value    It s a very simple process  so I m not sure you were really asking this

User · Answer

ezpz s answer is almost perfect  but I hope I can add a little more   Geo asked about time in milliseconds  this sounds like an integer quantity  and I wouldn t take the detour through floating-point land  Thus my approach would be   irb main  038 0 gt  t8   Time now   gt  Sun Nov 01 15 18 04  0100 2009 irb main  039 0 gt  t9   Time now   gt  Sun Nov 01 15 18 18  0100 2009 irb main  040 0 gt  dif   t9 - t8   gt  13 940166 irb main  041 0 gt   1000   dif  to i   gt  13940   Multiplying by an integer 1000 preserves the fractional number perfectly and may be a little faster too   If you re dealing with dates and times  you may need to use the DateTime class  This works similarly but the conversion factor is 24   3600   1000   86400000    I ve found DateTime s strptime and strftime functions invaluable in parsing and formatting date time strings  e g  to from logs   What comes in handy to know is    The formatting characters for these functions   H   M   S       are almost the same as for the C functions found on any Unix Linux system  and There are a few more  In particular   L does milliseconds

User · Answer

DateTime now strftime   Q     Example usage    gt  gt  DateTime now strftime   Q     gt   1541433332357    gt  gt  DateTime now strftime   Q   to i   gt  1541433332357

User · Answer

You can add a little syntax sugar to the above solution with the following   class Time   def to ms      self to f   1000 0  to i   end end  start time   Time now sleep 3  end time   Time now elapsed time   end time to ms - start time to ms      gt  3004

User · Answer

As stated already  you can operate on Time objects as if they were numeric  or floating point  values  These operations result in second resolution which can easily be converted    For example   def time diff milli start  finish      finish - start    1000 0 end  t1   Time now   arbitrary elapsed time t2   Time now  msecs   time diff milli t1  t2   You will need to decide whether to truncate that or not

[ruby] How do I get elapsed time in milliseconds in Ruby?

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