Get the current time, in milliseconds, in C?

Question

What is the equivalence of the Java's System.currentTimeMillis() in C?

Answer 1

Check time.h, perhaps something like the gettimeofday() function.

You can do something like

struct timeval now;
gettimeofday(&now, NULL);

Then you can extract time by getting values from now.tv_sec and now.tv_usec.

Answer 2

On Linux and other Unix-like systems, you should use clock_gettime(CLOCK_MONOTONIC). If this is not available (e.g. Linux 2.4), you can fall back to gettimeofday(). The latter has the drawback of being affected by clock adjustments.

On Windows, you can use QueryPerformanceCounter().

This code of mine abstracts all of the above into a simple interface that returns the number of milliseconds as an int64_t. Note that the millisecond values returned are intended only for relative use (e.g. timeouts), and are not relative to any particular time.