time - get time in seconds
#include <time.h> time_t time(time_t *tloc);
time() returns the time as the number of seconds since the Epoch, 1970-01-01 00:00:00 +0000 (UTC).
tloc is non-NULL, the return value is also stored in the memory pointed to by
On success, the value of time in seconds since the Epoch is returned. On error,
((time_t) -1) is returned, and
errno is set appropriately.
SVr4, 4.3BSD, C89, C99, POSIX.1-2001. POSIX does not specify any error conditions.
seconds since the Epoch using a formula that approximates the number of seconds between a specified time and the Epoch. This formula takes account of the facts that all years that are evenly divisible by 4 are leap years, but years that are evenly divisible by 100 are not leap years unless they are also evenly divisible by 400, in which case they are leap years. This value is not the same as the actual number of seconds between the time and the Epoch, because of leap seconds and because system clocks are not required to be synchronized to a standard reference. The intention is that the interpretation of seconds since the Epoch values be consistent; see POSIX.1-2008 Rationale A.4.15 for further rationale.
On Linux, a call to time() with
tloc specified as NULL cannot fail with the error EOVERFLOW, even on ABIs where
time_t is a signed 32-bit integer and the clock ticks past the time 2**31 (2038-01-19 03:14:08 UTC, ignoring leap seconds). (POSIX.1 permits, but does not require, the EOVERFLOW error in the case where the seconds since the Epoch will not fit in
time_t.) Instead, the behavior on Linux is undefined when the system time is out of the
time_t range. Applications intended to run after 2038 should use ABIs with
time_t wider than 32 bits.
Error returns from this system call are indistinguishable from successful reports that the time is a few seconds
before the Epoch, so the C library wrapper function never sets
errno as a result of this call.
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