time - get time in seconds
time_t time(time_t *tloc);
() returns the time as the number of seconds since the Epoch,
1970-01-01 00:00:00 +0000 (UTC).
is non-NULL, the return value is also stored in the memory
pointed to by tloc
On success, the value of time in seconds since the Epoch is returned. On error,
is returned, and errno
- tloc points outside your accessible address space
(but see BUGS).
- On systems where the C library time() wrapper
function invokes an implementation provided by the vdso(7) (so that
there is no trap into the kernel), an invalid address may instead trigger
a SIGSEGV signal.
SVr4, 4.3BSD, C89, C99, POSIX.1-2001. POSIX does not specify any error
POSIX.1 defines 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
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.
argument is obsolescent and should always be NULL in new code.
is NULL, the call cannot fail.
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