如何在Linux中實現毫秒精度的時間測量？

Obtaining Millisecond Precision Time Measurement in Linux

When working with time measurements in C++, the clock() function provides a convenient method to retrieve the current time in milliseconds on Windows systems. However, on Linux, clock() may provide less precise results, rounding the time to the nearest second.

In this case, the solution is to utilize the standard sys/time.h header and functions. The gettimeofday() function returns the current time of day as a timeval struct, which contains both seconds and microseconds since the Epoch. By subtracting the start time from the end time and converting the microseconds into milliseconds, we can obtain millisecond precision time measurements.

Here's an example code snippet that demonstrates how to use gettimeofday() to achieve millisecond precision time measurement:

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

int main()
{
    struct timeval start, end;
    long mtime, seconds, useconds;    

    gettimeofday(&start, NULL);
    usleep(2000); // Sleep for 2 milliseconds
    gettimeofday(&end, NULL);

    seconds  = end.tv_sec  - start.tv_sec;
    useconds = end.tv_usec - start.tv_usec;

    mtime = ((seconds) * 1000 + useconds/1000.0) + 0.5;

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

    return 0;
}

In this example, gettimeofday() is used to retrieve both the start and end times. The difference between the seconds and microseconds is calculated, and the result is converted into milliseconds with a precision up to 0.5 milliseconds.

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