NAME

       time - get time in seconds

SYNOPSIS

       #include <time.h>

       time_t time(time_t *tloc);

DESCRIPTION

       time()  returns  the  time  as  the number of seconds since the Epoch, 1970-01-01 00:00:00
       +0000 (UTC).

       If tloc is non-NULL, the return value is also stored in the memory pointed to by tloc.

RETURN VALUE

       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.

ERRORS

       EFAULT 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.

CONFORMING TO

       SVr4, 4.3BSD, C89, C99, POSIX.1-2001.  POSIX does not specify any error conditions.

NOTES

       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 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.

BUGS

       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.

       The  tloc  argument  is  obsolescent  and should always be NULL in new code.  When tloc is
       NULL, the call cannot fail.

   C library/kernel differences
       On some architectures, an implementation of time() is provided in the vdso(7).

SEE ALSO

       date(1), gettimeofday(2), ctime(3), ftime(3), time(7), vdso(7)

COLOPHON

       This page is part of release 4.15 of the Linux man-pages project.  A  description  of  the
       project,  information  about  reporting  bugs, and the latest version of this page, can be
       found at https://www.kernel.org/doc/man-pages/.