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DIFFTIME(3) Linux Programmer's Manual DIFFTIME(3)

difftime - calculate time difference

#include <time.h>
double difftime(time_t time1, time_t time0);

The difftime() function returns the number of seconds elapsed between time time1 and time time0, represented as a double. Each of the times is specified in calendar time, which means its value is a measurement (in seconds) relative to the Epoch, 1970-01-01 00:00:00 +0000 (UTC).

For an explanation of the terms used in this section, see attributes(7).
Interface Attribute Value
difftime () Thread safety MT-Safe

POSIX.1-2001, POSIX.1-2008, C89, C99, SVr4, 4.3BSD.

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.

date(1), gettimeofday(2), time(2), ctime(3), gmtime(3), localtime(3)

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2015-08-08 GNU