.\" Copyright (c) 1992 Drew Eckhardt (drew@cs.colorado.edu), March 28, 1992 .\" .\" %%%LICENSE_START(VERBATIM) .\" Permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" Permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" Since the Linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. The author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. The author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" Formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%LICENSE_END .\" .\" Modified by Michael Haardt .\" Modified Sat Jul 24 14:13:40 1993 by Rik Faith .\" Additions by Joseph S. Myers , 970909 .\" .TH TIME 2 2015-12-28 "Linux" "Linux Programmer's Manual" .SH NAME time \- get time in seconds .SH SYNOPSIS .B #include .sp .BI "time_t time(time_t *" tloc ); .SH DESCRIPTION .BR time () returns the time as the number of seconds since the Epoch, 1970-01-01 00:00:00 +0000 (UTC). If .I tloc is non-NULL, the return value is also stored in the memory pointed to by .IR tloc . .SH RETURN VALUE On success, the value of time in seconds since the Epoch is returned. On error, \fI((time_t)\ \-1)\fP is returned, and \fIerrno\fP is set appropriately. .SH ERRORS .TP .B EFAULT .I tloc points outside your accessible address space (but see BUGS). On systems where the C library .BR time () wrapper function invokes an implementation provided by the .BR vdso (7) (so that there is no trap into the kernel), an invalid address may instead trigger a .B SIGSEGV signal. .SH CONFORMING TO SVr4, 4.3BSD, C89, C99, POSIX.1-2001. .\" .br .\" Under 4.3BSD, this call is obsoleted by .\" .BR gettimeofday (2). POSIX does not specify any error conditions. .SH NOTES POSIX.1 defines .I 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 .BR time () with .I tloc specified as NULL cannot fail with the error .BR EOVERFLOW , even on ABIs where .I 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 .B EOVERFLOW error in the case where the seconds since the Epoch will not fit in .IR time_t .) Instead, the behavior on Linux is undefined when the system time is out of the .I time_t range. Applications intended to run after 2038 should use ABIs with .I time_t wider than 32 bits. .SH BUGS Error returns from this system call are indistinguishable from successful reports that the time is a few seconds .I before the Epoch, so the C library wrapper function never sets .I errno as a result of this call. The .I tloc argument is obsolescent and should always be NULL in new code. When .I tloc is NULL, the call cannot fail. .SH SEE ALSO .BR date (1), .BR gettimeofday (2), .BR ctime (3), .BR ftime (3), .BR time (7), .BR vdso (7) .SH COLOPHON This page is part of release 4.10 of the Linux .I 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/.