1.\" Copyright (c) 1989, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" This code is derived from software contributed to Berkeley by 5.\" the American National Standards Committee X3, on Information 6.\" Processing Systems. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice, this list of conditions and the following disclaimer in the 15.\" documentation and/or other materials provided with the distribution. 16.\" 3. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)time.3 8.1 (Berkeley) 6/4/93 33.\" 34.Dd April 14, 2022 35.Dt TIME 3 36.Os 37.Sh NAME 38.Nm time 39.Nd get time of day 40.Sh LIBRARY 41.Lb libc 42.Sh SYNOPSIS 43.In time.h 44.Ft time_t 45.Fn time "time_t *tloc" 46.Sh DESCRIPTION 47The 48.Fn time 49function 50returns the value of time in seconds since 0 hours, 0 minutes, 510 seconds, January 1, 1970, Coordinated Universal Time (UTC). 52If an error occurs, 53.Fn time 54returns the value 55.Po Vt time_t Pc Ns \-1 . 56.Pp 57The return value is also stored in 58.No \&* Ns Va tloc , 59provided that 60.Va tloc 61is non-null. 62.Sh ERRORS 63The 64.Fn time 65function may fail for any of the reasons described in 66.Xr clock_gettime 2 . 67.Sh SEE ALSO 68.Xr clock_gettime 2 , 69.Xr gettimeofday 2 , 70.Xr ctime 3 71.Sh STANDARDS 72The 73.Nm 74function conforms to 75.St -p1003.1-2008 . 76.Sh HISTORY 77The 78.Fn time 79system call first appeared in 80.At v1 . 81Through the 82.At v3 , 83it returned 60 Hz ticks since an epoch that changed occasionally, because it 84was a 32-bit value that overflowed in a little over 2 years. 85.Pp 86In 87.At v4 88the granularity of the return value was reduced to whole seconds, 89delaying the aforementioned overflow until 2038. 90.Pp 91.At v7 92introduced the 93.Fn ftime 94system call, which returned time at a millisecond level, 95though retained the 96.Fn gtime 97system call (exposed as 98.Fn time 99in userland). 100.Fn time 101could have been implemented as a wrapper around 102.Fn ftime , 103but that wasn't done. 104.Pp 105.Bx 4.1c 106implemented a higher-precision time function 107.Fn gettimeofday 108to replace 109.Fn ftime 110and reimplemented 111.Fn time 112in terms of that. 113.Pp 114Since 115.Fx 9 116the implementation of 117.Fn time 118uses 119.Fn clock_gettime "CLOCK_SECOND" 120instead of 121.Fn gettimeofday 122for performance reasons. 123.Sh BUGS 124Neither 125.St -isoC-99 126nor 127.St -p1003.1-2001 128requires 129.Fn time 130to set 131.Va errno 132on failure; thus, it is impossible for an application to distinguish 133the valid time value \-1 (representing the last UTC second of 1969) 134from the error return value. 135.Pp 136Systems conforming to earlier versions of the C and POSIX 137standards (including older versions of 138.Fx ) 139did not set 140.No \&* Ns Va tloc 141in the error case. 142