C get milliseconds timestamp

from https://stackoverflow.com/questions/3756323/how-to-get-the-current-time-in-milliseconds-from-c-in-linux

#include <sys/time.h>

long current_timestamp()
{
    struct timeval te;
    gettimeofday(&te, NULL); // get current time
    long long milliseconds = te.tv_sec*1000LL + te.tv_usec/1000; // caculate milliseconds
    printf("milliseconds: %lld\n", milliseconds);
    return milliseconds;
}