DIFFTIME(3) Linux Programmer s Manual DIFFTIME(3)
NAME difftime - calculate time difference
SYNOPSIS #include <time.h>
double difftime(time_t time1, time_t time0);
DESCRIPTION The difftime() function returns the number of seconds elapsed between time time1 and time time0, represented as a double. The two times are specified in calendar time, which represents the time elapsed since the Epoch (00:00:00 on January 1, 1970, Coordinated Universal Time (UTC)).
CONFORMING TO SVr4, 4.3BSD, C99
NOTES On a POSIX system, time_t is an arithmetic type, and one could just define
#define difftime(t1,t0) (double)(t1 - t0)
when the possible overflow in the subtraction is not a concern. On other systems, the data type time_t might use some other encoding where subtraction doesnt work directly.
CONFORMING TO SVr4, 4.3BSD, POSIX.1-2001.
SEE ALSO date(1), gettimeofday(2), time(2), ctime(3), gmtime(3), localtime(3)
GNU 2002-02-28 DIFFTIME(3)