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NAMEtime —
get time of day
LIBRARYStandard C Library (libc, -lc)SYNOPSIS#include <time.h>
time_t
DESCRIPTIONThetime () function returns the value of time in seconds
since 0 hours, 0 minutes, 0 seconds, January 1, 1970, Coordinated Universal
Time (UTC). If an error occurs, time () returns the
value (time_t)-1.
The return value is also stored in *tloc, provided that tloc is non-null. ERRORSThetime () function may fail for any of the reasons
described in
gettimeofday(2).
SEE ALSOclock_gettime(2), gettimeofday(2), ctime(3)STANDARDSThetime function conforms to IEEE Std
1003.1-2008 (“POSIX.1”).
HISTORYThetime () system call first appeared in
Version 1 AT&T UNIX. Through the
Version 3 AT&T UNIX, it returned 60 Hz
ticks since an epoch that changed occasionally, because it was a 32-bit value
that overflowed in a little over 2 years.
In Version 4 AT&T UNIX the granularity of the return value was reduced to whole seconds, delaying the aforementioned overflow until 2038. Version 7 AT&T UNIX introduced
the 4.1cBSD implemented a higher-precision
time function Since FreeBSD 9 the implementation of
BUGSNeither ISO/IEC 9899:1999 (“ISO C99”) nor IEEE Std 1003.1-2001 (“POSIX.1”) requirestime () to set errno on failure;
thus, it is impossible for an application to distinguish the valid time value
-1 (representing the last UTC second of 1969) from the error return value.
Systems conforming to earlier versions of the C and POSIX standards (including older versions of FreeBSD) did not set *tloc in the error case.
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