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TIME(3)			    Library Functions Manual		       TIME(3)

NAME
       time -- get time	of day

LIBRARY
       Standard	C Library (libc, -lc)

SYNOPSIS
       #include	<time.h>

       time_t
       time(time_t *tloc);

DESCRIPTION
       The time() 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.

ERRORS
       The  time()  function  may  fail	 for  any  of the reasons described in
       clock_gettime(2).

SEE ALSO
       clock_gettime(2), gettimeofday(2), ctime(3)

STANDARDS
       The time	function conforms to IEEE Std 1003.1-2008 ("POSIX.1").

HISTORY
       The time() 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 ftime() system call, which  returned
       time  at	 a  millisecond	level, though retained the gtime() system call
       (exposed	as time() in userland).	 time()	could have been	implemented as
       a wrapper around	ftime(), but that wasn't done.

       4.1cBSD implemented a higher-precision time function gettimeofday()  to
       replace ftime() and reimplemented time()	in terms of that.

       Since	FreeBSD	   9	     the   implementation   of	 time()	  uses
       clock_gettime(CLOCK_SECOND) instead of gettimeofday()  for  performance
       reasons.

BUGS
       Neither	 ISO/IEC  9899:1999  ("ISO  C99")  nor	IEEE  Std  1003.1-2001
       ("POSIX.1") requires time() to set errno	on failure; thus, it is	impos-
       sible for an application	to distinguish the valid time value -1 (repre-
       senting 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.

FreeBSD	13.2			April 14, 2022			       TIME(3)
NAME | LIBRARY | SYNOPSIS | DESCRIPTION | ERRORS | SEE ALSO | STANDARDS | HISTORY | BUGS

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