Time stamp in the C programming language

Question

How do I stamp two times t1 and t2 and get the difference in milliseconds in C

User · Answer

Standard C99    include  lt time h gt   time t t0   time 0          time t t1   time 0   double datetime diff ms   difftime t1  t0    1000    clock t c0   clock           clock t c1   clock    double runtime diff ms    c1 - c0    1000    CLOCKS PER SEC    The precision of the types is implementation-defined  ie the datetime difference might only return full seconds

User · Answer

U can try routines in c time library  time h   Plus take a look at the clock   in the same lib  It gives the clock ticks since the prog has started  But you can save its value before the operation you want to concentrate on  and then after that operation capture the cliock ticks again and find the difference between then to get the time difference

User · Answer

Returns the current time      char  time stamp     char  timestamp    char   malloc sizeof char    16   time t ltime  ltime time NULL   struct tm  tm  tm localtime  amp ltime    sprintf timestamp   04d 02d 02d 02d 02d 02d   tm- gt tm year 1900  tm- gt tm mon       tm- gt tm mday  tm- gt tm hour  tm- gt tm min  tm- gt tm sec   return timestamp      int main     printf   Timestamp   s n  time stamp     return 0       Output  Timestamp  20110912130940    2011 Sep 12 13 09 40

User · Answer

This will give you the time in seconds   microseconds   include  lt sys time h gt  struct timeval tv  gettimeofday  amp tv NULL   tv tv sec    seconds tv tv usec    microseconds

User · Answer

Also making aware of interactions between clock   and usleep    usleep   suspends the program  and clock   only measures the time the program is running    If might be better off to use gettimeofday   as mentioned here

User · Answer

If you want to find elapsed time  this method will work as long as you don t reboot the computer between the start and end   In Windows  use GetTickCount     Here s how   DWORD dwStart   GetTickCount            process you want to measure elapsed time for     DWORD dwElapsed   GetTickCount   - dwStart    dwElapsed is now the number of elapsed milliseconds   In Linux  use clock   and CLOCKS PER SEC to do about the same thing   If you need timestamps that last through reboots or across PCs  which would need quite good syncronization indeed   then use the other methods  gettimeofday      Also  in Windows at least you can get much better than standard time resolution   Usually  if you called GetTickCount   in a tight loop  you d see it jumping by 10-50 each time it changed   That s because of the time quantum used by the Windows thread scheduler   This is more or less the amount of time it gives each thread to run before switching to something else   If you do a   timeBeginPeriod 1     at the beginning of your program or process and a   timeEndPeriod 1     at the end  then the quantum will change to 1 ms  and you will get much better time resolution on the GetTickCount   call   However  this does make a subtle change to how your entire computer runs processes  so keep that in mind   However  Windows Media Player and many other things do this routinely anyway  so I don t worry too much about it   I m sure there s probably some way to do the same in Linux  probably with much better control  or maybe with sub-millisecond quantums  but I haven t needed to do that yet in Linux

User · Answer

Use  Arkaitz Jimenez s code to get two timevals    include  lt sys time h gt        struct timeval tv1  tv2  diff      get the first time  gettimeofday  amp tv1  NULL       do whatever it is you want to time            get the second time  gettimeofday  amp tv2  NULL       get the difference   int result   timeval subtract  amp diff   amp tv1   amp tv2       the difference is storid in diff now    Sample code for timeval subtract can be found at this web site       Subtract the  struct timeval  values X and Y      storing the result in RESULT      Return 1 if the difference is negative  otherwise 0        int  timeval subtract  result  x  y        struct timeval  result   x   y           Perform the carry for the later subtraction by updating y        if  x- gt tv usec  lt  y- gt tv usec         int nsec    y- gt tv usec - x- gt tv usec    1000000   1       y- gt tv usec -  1000000   nsec       y- gt tv sec    nsec          if  x- gt tv usec - y- gt tv usec  gt  1000000         int nsec    x- gt tv usec - y- gt tv usec    1000000       y- gt tv usec    1000000   nsec       y- gt tv sec -  nsec              Compute the time remaining to wait        tv usec is certainly positive        result- gt tv sec   x- gt tv sec - y- gt tv sec     result- gt tv usec   x- gt tv usec - y- gt tv usec         Return 1 if result is negative        return x- gt tv sec  lt  y- gt tv sec

User · Answer

Use gettimeofday   or better clock gettime

User · Answer

how about this solution  I didn t see anything like this in my search  I am trying to avoid division and make solution simpler      struct timeval cur time1  cur time2  tdiff      gettimeofday  amp cur time1 NULL      sleep 1      gettimeofday  amp cur time2 NULL       tdiff tv sec   cur time2 tv sec - cur time1 tv sec     tdiff tv usec   cur time2 tv usec    1000000 - cur time1 tv usec       while tdiff tv usec  gt  1000000             tdiff tv sec          tdiff tv usec -  1000000        printf  updated tdiff tv sec  ld tv usec  ld n  tdiff tv sec  tdiff tv usec            printf  end tdiff tv sec  ld tv usec  ld n  tdiff tv sec  tdiff tv usec

[c] Time stamp in the C programming language

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