How to Achieve Milliseconds-Precise Timing in C on Linux Without External Libraries?

Milliseconds-Precise Timing in C on Linux

Originally asking about why clock() returns time in milliseconds on Windows but only seconds on Linux, the questioner seeks a solution for obtaining millisecond-level time accuracy without relying on third-party libraries like Boost or Qt.

Solution Using gettimeofday()

The solution lies in leveraging the gettimeofday() function present in the standard C library. Here's how to implement it:

1. Include necessary headers:

   #include <sys/time.h>
   #include <stdio.h>
   #include <unistd.h>

2. Define a struct timeval to store the seconds and microseconds:

   struct timeval start, end;

3. Get the start time:

   gettimeofday(&start, NULL);

4. Specify a delay in microseconds using usleep() (replace with your desired delay):

   usleep(2000);

5. Get the end time:

   gettimeofday(&end, NULL);

6. Calculate the elapsed time:

   long mtime, seconds, useconds;    
   
   seconds  = end.tv_sec  - start.tv_sec;
   useconds = end.tv_usec - start.tv_usec;
   
   mtime = ((seconds) * 1000 + useconds/1000.0) + 0.5;

7. Print the elapsed time in milliseconds:

   printf("Elapsed time: %ld milliseconds\n", mtime);

This code snippet utilizes gettimeofday() to obtain the time in microseconds, ensuring millisecond-level precision. It serves as a robust and standard solution for acquiring accurate time measurements in C on Linux.

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