1.\" $NetBSD: time.3,v 1.17 2024/04/28 22:57:16 rillig Exp $ 2.\" 3.\" Copyright (c) 1989, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" This code is derived from software contributed to Berkeley by 7.\" the American National Standards Committee X3, on Information 8.\" Processing Systems. 9.\" 10.\" Redistribution and use in source and binary forms, with or without 11.\" modification, are permitted provided that the following conditions 12.\" are met: 13.\" 1. Redistributions of source code must retain the above copyright 14.\" notice, this list of conditions and the following disclaimer. 15.\" 2. Redistributions in binary form must reproduce the above copyright 16.\" notice, this list of conditions and the following disclaimer in the 17.\" documentation and/or other materials provided with the distribution. 18.\" 3. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" @(#)time.3 8.1 (Berkeley) 6/4/93 35.\" 36.Dd April 29, 2024 37.Dt TIME 3 38.Os 39.Sh NAME 40.Nm time 41.Nd get time of day 42.Sh LIBRARY 43.Lb libc 44.Sh SYNOPSIS 45.In time.h 46.Ft time_t 47.Fn time "time_t *tloc" 48.Sh DESCRIPTION 49The 50.Fn time 51function 52returns the value of time in seconds since 0 hours, 0 minutes, 530 seconds, January 1, 1970, Coordinated Universal Time. 54.Pp 55If 56.Fa tloc 57is not a null pointer, a copy of the time value is saved in 58.Fa *tloc . 59.Pp 60Upon successful completion, 61.Fn time 62returns the value of time. 63Otherwise a value of 64.Po 65.Po Fa time_t Pc Ns \-1 66.Pc 67is returned and the global variable 68.Va errno 69is set to indicate the error. 70.Sh ERRORS 71No errors are defined. 72.Sh SEE ALSO 73.Xr gettimeofday 2 , 74.Xr ctime 3 75.Sh STANDARDS 76The 77.Fn time 78function conforms to 79.St -p1003.1-90 . 80.Sh HISTORY 81A 82.Fn time 83function appeared in 84.At v2 . 85It returned a 32-bit value measuring sixtieths of a second, leading to 86rollover every 2.26 years. 87In 88.At v6 , 89the precision of 90.Fn time 91was changed to seconds, allowing 135.6 years between rollovers. 92.Pp 93In 94.Nx 6.0 95the 96.Vt time_t 97type was changed to be 64 bits wide, including on 32-bit machines, 98making rollover a concern for the far distant future only. 99Note however that any code making the incorrect assumption that 100.Vt time_t 101is the same as 102.Vt long 103will fail on 32-bit machines in 2038. 104