Unix and Linux keep track of time in seconds before or after the epoch, which is defined as midnight, January 1, 1970 UTC. Positive time values are after the epoch; negative time values are before the epoch. In order to provide processes with the current time, Linux, like all versions of Unix, provides a system call called
#include <time.h> time_t time(time_t *t);
time() returns the number of seconds since the epoch, and if
t is non-null, it also fills in
t with the number of seconds since the epoch.
Some problems require higher resolution. Linux provides another system call,
gettimeofday(), which provides more information:
#include <sys/time.h> #include <unistd.h> int gettimeofday(struct ...