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author | Gordon Bergling <gbe@FreeBSD.org> | 2022-04-14 08:04:14 +0000 |
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committer | Gordon Bergling <gbe@FreeBSD.org> | 2022-04-22 14:36:36 +0000 |
commit | 6b642cf5c8742a3c307772321e0f5e4153a0b1ad (patch) | |
tree | fd45a96b6cf19f79c2f604c13769b2080f4b2daf /stand | |
parent | 283d1b98251b7ff1e53b43d3f0264c2a087f207b (diff) | |
download | src-6b642cf5c8742a3c307772321e0f5e4153a0b1ad.tar.gz src-6b642cf5c8742a3c307772321e0f5e4153a0b1ad.zip |
time(3): Refine history in the manual page
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.
With most valuable input from Warner (imp@).
Reviewed by: 0mp, jilles, imp
Approved by: re (gjb)
Differential Revision: https://reviews.freebsd.org/D34751
(cherry picked from commit 3e0f3678eca7c3f296b9f702992737356f1792da)
Diffstat (limited to 'stand')
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