.\" Copyright (c) 2006 by Michael Kerrisk <mtk.manpages@gmail.com>
.\"
.\" 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.\" manual page may be incorrect or out-of-date.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.
.\"
.\" 2008-06-24, mtk: added some details about where jiffies come into
.\"     play; added section on high-resolution timers.
.\"
.\" Japanese Version Copyright (c) 2006 Yuichi SATO
.\"         all rights reserved.
.\" Translated 2006-07-23 by Yuichi SATO <ysato444@yahoo.co.jp>, LDP v2.36
.\" Updated 2007-05-04, Akihiro MOTOKI <amotoki@dd.iij4u.or.jp>, LDP v2.44
.\" Updated 2008-08-10, Akihiro MOTOKI <amotoki@dd.iij4u.or.jp>, LDP v3.05
.\"
.TH TIME 7 2009-02-10 "Linux" "Linux Programmer's Manual"
.SH ̾
time \- ֤ȥޤγ
.SH 
.SS "» (real time) ȥץ"
\fI»\fRϡλפä֤롣
λȤϡɸŪʻ
(ε (Epoch) ȥ򻲾) 䡢
ץΰˤ벿餫λ (㤨Сϻ) Ǥ
.RI ( "в" )

\fIץ\fRϡץˤäƻȤ줿 CPU ֤롣
¿ξ硢\fI桼\fR֤\fIƥ\fR֤ʬ롣
桼 CPU ֤ϡɤ桼⡼ɤǼ¹ԤΤ˻Ȥä֤Ǥ롣
ƥ CPU ֤ϡΥץΤ
ͥ뤬ƥ⡼ɤǼ¹ԤΤ˻Ȥä֤Ǥ
(㤨Сƥॳ¹ԤΤ˻Ȥä)
.BR time (1)
ޥɤϥץμ¹Ԥ񤵤줿 CPU ֤פΤ˻Ѥ롣
ץϡȤ񤷤 CPU ֤
.BR times (2),
.BR getrusage (2),
.BR clock (3)
ȤäƷפ뤳ȤǤ롣
.SS ϡɥå
¿Υԥ塼 (ӤǶư) ϡɥåäƤ롣
ͥϵư˥եȥå뤿
ϡɥåɤ߹ࡣ
ܤϡ
.BR rtc (4)

.BR hwclock (8)
򻲾Ȥ뤳ȡ
.SS "եȥå, HZ, Jiffy"
ॢȤꤷ (㤨
.BR select (2),
.BR sigtimedwait (2))
.\" semtimedop(), mq_timedwait(), io_getevents(), poll() Ʊ futex Ǥꡢ
.\" ää sem_timedwait() Ϲ٥ޤѤƤ褦Ǥ롣
CPU ֤¬ (㤨
.BR getrusage (2)) ͡ʥƥॳ٤
.I եȥå
ʬǽ (resolution) ¤롣
եȥåȤϡͥ뤬
.I jiffy
ñ̤ǻ֤¬륯åΤȤǤ롣
jiffy 礭ϥͥ
.I HZ
ͤǷꤵ롣

.I HZ
ͤϥͥΥСȥϡɥץåȥեǰۤʤ롣
i386 ξϰʲ̤Ǥ:
2.4.x ȤΥͥǤϡHZ  100 ǤäΤǡ
jiffy ͤ 0.01 äˤʤäƤ
2.6.0 ʹߤǤϡHZ  1000 䤵줿Τǡjiffy ͤ 0.001 äǤ롣
ͥ 2.6.13 ʹߤǤϡHZ ͤϥͥѥ᡼ˤʤꡢ
100, 250 (ǥե), 1000 ȤͤˤǤ롣
줾 jiffy ͤ 0.01, 0.004, 0.001 äˤʤ롣
ͥ 2.6.20 ʹߤǤϡ300 ѤǤ褦ˤʤäƤ롣
300 ϰŪʱե졼졼ȤθܿǤ (PAL, 25HZ; NTSC, 30HZ)

.BR times (2)
ƥॳüʥǤꡢ
Υƥॳϥͥ
.I USER_HZ
줿γ٤ǻ֤𤹤롣
桼֤Υץꥱ
.I sysconf(_SC_CLK_TCK)
ȤäƤͤΤ뤳ȤǤ롣
.\" glibc gets this info with a little help from the ELF loader;
.\" see glibc elf/dl-support.c and kernel fs/binfmt_elf.c.
.\"
.SS "٥"
Linux 2.6.21 Ǥϡޤ䥹꡼״ϢΥƥॳ٤
jiffy Υˤ¤Ƥ

Linux 2.6.21 ʹߤǤϡLinux Ϲ٥ (high-resolution timers; HRTs)
򥵥ݡȤƤꡢ
.B CONFIG_HIGH_RES_TIMERS
Ǥ롣
٥ޤ򥵥ݡȤƤ륷ƥǤϡޤȥ꡼״ϢΥƥॳ
٤ϤϤ jiffy 󤵤뤳ȤϤʤ
ϡɥ¤٤Ȥʤ
(ǶΥϡɥǤϥޥñ̤٤ŪǤ)
٥ޤݡȤƤ뤫ϡ
.BR clock_getres (2)
ƤӽФʬǽǧ뤫
.I /proc/timer_list
 "resolution" ȥ򻲾Ȥ뤫ȽǤǤ롣

٥ޤϤ٤ƤΥϡɥƥǥݡȤƤ
ǤϤʤ (бƤ륢ƥ x86, arm, powerpc Ǥ)
.SS ""
Unix ƥϻ \fI\fR ÿɽ롣
 1970 ǯ 1  1 ī 0:00:00 UTC 롣

ץ \fI\fR 
.BR gettimeofday (2)
ȤäƷפ뤳ȤǤ롣
δؿϵηв֤ (äȥޥä) ֤
.BR time (2)
Ʊͤξ󶡤뤬Ǥᤤä٤ʤ
ƥ
.BR settimeofday (2)
ѹǤ롣
.SS "̤λ"
饤֥ؿˤ
.I tm
ι¤ΤȤΤ롣
ι¤Τ\fI̤λ\fRɽ
̡ͤ (ǯʬäʤ) ʬƳǼ롣
ι¤Τ
.BR ctime (3)
˵ҤƤꡢ̤λѴ
ؿˤĤƤ⵭ҤƤ롣
̤λɽǽʸѴؿˤĤƤϡ
.BR ctime (3),
.BR strftime (3),
.BR strptime (3)
˵ҤƤ롣
.SS "ޤΥ꡼פ"
͡ʥƥॳȴؿˤꡢꤵ줿λ֡
ץϥ꡼ (¹Ԥ) 뤳ȤǽǤ롣
.BR nanosleep (2),
.BR clock_nanosleep (2),
.BR sleep (3)
򻲾Ȥ뤳ȡ

͡ʥƥॳˤꡢץϾΤ
֤ͭλ륿ޤǤ롣
ޤץȤƷֳ֤֤ǤΤ⤢롣
.BR alarm (2),
.BR getitimer (2),
.BR timerfd_create (2),
.BR timer_create (2)
򻲾Ȥ뤳ȡ
.SH Ϣ
.BR date (1),
.BR time (1),
.BR adjtimex (2),
.BR alarm (2),
.BR clock_gettime (2),
.BR clock_nanosleep (2),
.BR getitimer (2),
.BR getrlimit (2),
.BR getrusage (2),
.BR gettimeofday (2),
.BR nanosleep (2),
.BR stat (2),
.BR time (2),
.BR timer_create (2),
.BR timerfd_create (2),
.BR times (2),
.BR utime (2),
.BR adjtime (3),
.BR clock (3),
.BR clock_getcpuclockid (3),
.BR ctime (3),
.BR pthread_getcpuclockid (3),
.BR sleep (3),
.BR strftime (3),
.BR strptime (3),
.BR timeradd (3),
.BR usleep (3),
.BR rtc (4),
.BR hwclock (8)