[linuxjm/LDP_man-pages.git] / draft / man2 / nanosleep.2

.\" Hey Emacs! This file is -*- nroff -*- source.
.\"
.\" Copyright (C) Markus Kuhn, 1996
.\" and Copyright (C) Linux Foundation, 2008, written by Michael Kerrisk
.\"     <mtk.manpages@gmail.com>
.\"
.\" This is free documentation; you can redistribute it and/or
.\" modify it under the terms of the GNU General Public License as
.\" published by the Free Software Foundation; either version 2 of
.\" the License, or (at your option) any later version.
.\"
.\" The GNU General Public License's references to "object code"
.\" and "executables" are to be interpreted as the output of any
.\" document formatting or typesetting system, including
.\" intermediate and printed output.
.\"
.\" This manual is distributed in the hope that it will be useful,
.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
.\" GNU General Public License for more details.
.\"
.\" You should have received a copy of the GNU General Public
.\" License along with this manual; if not, write to the Free
.\" Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111,
.\" USA.
.\"
.\" 1996-04-10  Markus Kuhn <mskuhn@cip.informatik.uni-erlangen.de>
.\"             First version written
.\" Modified, 2004-10-24, aeb
.\" 2008-06-24, mtk
.\"     Minor rewrites of some parts.
.\"     NOTES: describe case where clock_nanosleep() can be preferable.
.\"     NOTES: describe CLOCK_REALTIME versus CLOCK_NANOSLEEP
.\"     Replace crufty discussion of HZ with a pointer to time(7).
.\"
.\" Japanese Version Copyright (c) 1997 HANATAKA Shinya
.\"         all rights reserved.
.\" Translated, 1997-02-23, HANATAKA Shinya <hanataka@abyss.rim.or.jp>
.\" Updated 1999-02-27, HANATAKA Shinya <hanataka@abyss.rim.or.jp>
.\" Updated 2003-09-15, Akihiro MOTOKI <amotoki@dd.iij4u.or.jp>
.\" Updated 2005-02-10, Akihiro MOTOKI
.\" Updated 2006-07-23, Akihiro MOTOKI, LDP v2.36
.\" Updated 2006-08-13, Akihiro MOTOKI, LDP v2.39
.\" Updated 2008-08-08, Akihiro MOTOKI, LDP v3.05
.\"
.\"WORD:        puase                   Ää»ß
.\"WORD:        sleep                   Ää»ß
.\"WORD:        signal                  ¥·¥°¥Ê¥ë
.\"WORD:        NULL                    NULL
.\"WORD:        block                   ¶Ø»ß(block)
.\"WORD:        kernel                  ¥«¡¼¥Í¥ë
.\"WORD:        real-time               ¥ê¥¢¥ë¡¦¥¿¥¤¥à
.\"WORD:        schedule                ¥¹¥±¥¸¥å¡¼¥ë
.\"WORD:        busy wait               ¥Ó¥·¡¼¡¦¥¦¥§¥¤¥È
.\"
.TH NANOSLEEP 2 2009-01-19 "Linux" "Linux Programmer's Manual"
.\"O .SH NAME
.SH ̾Á°
.\"O nanosleep \- high-resolution sleep
nanosleep \- ¹âÀºÅ٤ʥ¹¥ê¡¼¥×
.\"O .SH SYNOPSIS
.SH ½ñ¼°
.B #include <time.h>
.sp
.BI "int nanosleep(const struct timespec *" req ", struct timespec *" rem );
.sp
.in -4n
.\"O Feature Test Macro Requirements for glibc (see
.\"O .BR feature_test_macros (7)):
glibc ¸þ¤±¤Îµ¡Ç½¸¡ºº¥Þ¥¯¥í¤ÎÍ×·ï
.RB ( feature_test_macros (7)
»²¾È):
.in
.sp
.BR nanosleep ():
_POSIX_C_SOURCE\ >=\ 199309L
.\"O .SH DESCRIPTION
.SH ÀâÌÀ
.\"O .BR nanosleep ()
.\"O suspends the execution of the calling thread
.\"O until either at least the time specified in
.\"O .IR *req
.\"O has elapsed, or the delivery of a signal
.\"O that triggers the invocation of a handler in the calling thread or
.\"O that terminates the process.
.BR nanosleep ()
¤Ï¡¢¾¯¤Ê¤¯¤È¤â
.I *req
¤Ç»ØÄꤵ¤ì¤¿»þ´Ö¤Î´Ö¡¢¥×¥í¥°¥é¥à¤Î¼Â¹Ô¤òÃٱ䤵¤»¤ë¡£
.BR nanosleep ()
¤Ï¡¢¸Æ¤Ó½Ð¤·¤¿¥¹¥ì¥Ã¥É¤Î¼Â¹Ô¤ò¡¢
¾¯¤Ê¤¯¤È¤â
.I *req
¤Ç»ØÄꤵ¤ì¤¿»þ´Ö¤Î´Ö¡¢¤â¤·¤¯¤Ï¸Æ¤Ó½Ð¤·¤¿¥¹¥ì¥Ã¥É¤Ç¥Ï¥ó¥É¥é¤Îµ¯Æ°¤Î
¤­¤Ã¤«¤±¤È¤Ê¤ë¥·¥°¥Ê¥ë¡¢¤Þ¤¿¤Ï¥×¥í¥»¥¹¤ò½ªÎ»¤µ¤»¤ë¥·¥°¥Ê¥ë¤ÎÇÛÁ÷¤¬
¹Ô¤ï¤ì¤ë¤Þ¤Ç°ì»þÄä»ß¤¹¤ë¡£

.\"O If the call is interrupted by a signal handler,
.\"O .BR nanosleep ()
.\"O returns \-1, sets \fIerrno\fP to
.\"O .BR EINTR ,
.\"O and writes the remaining time into the structure pointed to by
.\"O .I rem
.\"O unless
.\"O .I rem
.\"O is NULL.
¸Æ¤Ó½Ð¤·¤¬¥·¥°¥Ê¥ë¥Ï¥ó¥É¥é¤Ë¤è¤ê³ä¤ê¹þ¤Þ¤ì¤¿¾ì¹ç¡¢
.BR nanosleep
¤Ï \-1 ¤òÊÖ¤·¡¢
.I errno
¤Ë
.B EINTR
¤òÀßÄꤷ¡¢
.I rem
¤¬ NULL ¤Ç¤Ê¤±¤ì¤Ð
»Ä¤ê¤Î»þ´Ö¤ò
.I rem
¤¬»Ø¤¹¹½Â¤ÂΤ˳ÊǼ¤¹¤ë¡£
.\"O The value of
.\"O .I *rem
.\"O can then be used to call
.\"O .BR nanosleep ()
.\"O again and complete the specified pause (but see NOTES).
.I *rem
¤ÎÃͤò»È¤¦¤È¡¢
.BR nanosleep ()
¤ò¤â¤¦°ìÅٸƤӽФ·¤Æ¡¢»ØÄꤷ¤¿»þ´Ö¤ÎÄä»ß¤ò
´°Î»¤µ¤»¤ë¤³¤È¤¬¤Ç¤­¤ë (⤷¡¢¡ÖÃí°Õ¡×¤ÎÀá¤ò»²¾È¤Î¤³¤È)¡£

.\"O The structure
.\"O .I timespec
.\"O is used to specify intervals of time with nanosecond precision.
.\"O It is defined as follows:
¥Ê¥ÎÉùï¤ß¤Î»þ´Ö´Ö³Ö¤ò»ØÄꤹ¤ë¤Î¤Ë
.I timespec
¹½Â¤ÂΤ¬»ÈÍѤµ¤ì¤ë¡£¤³¤Î¹½Â¤ÂΤϼ¡¤Î¤è¤¦¤ËÄêµÁ¤µ¤ì¤Æ¤¤¤ë¡£
.sp
.in +4n
.nf
.\"O struct timespec {
.\"O     time_t tv_sec;        /* seconds */
.\"O     long   tv_nsec;       /* nanoseconds */
    time_t tv_sec;        /* ÉÃ */
    long   tv_nsec;       /* ¥Ê¥ÎÉà */
};
.fi
.in
.PP
.\"O The value of the nanoseconds field must be in the range 0 to 999999999.
¥Ê¥ÎÉäΥե£¡¼¥ë¥É¤ÎÃÍ¤Ï 0 ¤«¤é 999999999 ¤ÎÈϰϤˤʤ±¤ì¤Ð¤Ê¤é¤Ê¤¤¡£

.\"O Compared to
.\"O .BR sleep  (3)
.\"O and
.\"O .BR usleep (3),
.\"O .BR nanosleep ()
.\"O has the following advantages:
.\"O it provides a higher resolution for specifying the sleep interval;
.\"O POSIX.1 explicitly specifies that it
.\"O does not interact with signals;
.\"O and it makes the task of resuming a sleep that has been
.\"O interrupted by a signal handler easier.
.BR sleep  (3)
¤ä
.BR usleep (3)
¤ËÈæ¤Ù¤ë¤È
.BR nanosleep ()
¤Ë¤Ï°Ê²¼¤Î¤è¤¦¤ÊÍøÅÀ¤¬¤¢¤ë:
Ää»ß´ü´Ö¤Î»ØÄê¤Ë´Ø¤·¤Æ¹â¤¤»þ´Öʬ²òǽ¤¬Ä󶡤µ¤ì¤Æ¤¤¤ë¡£
¥·¥°¥Ê¥ë¤È¸ß¤¤¤Ë±Æ¶Á¤òµÚ¤Ü¤¹¤³¤È¤¬¤Ê¤¤¤È
POSIX.1 ¤ÇÌÀ¼¨Åª¤Ëµ¬Äꤵ¤ì¤Æ¤¤¤ë¡£
¥·¥°¥Ê¥ë¥Ï¥ó¥É¥é¤Ë¤è¤Ã¤Æ³ä¤ê¹þ¤Þ¤ì¤¿ºÝ¤Ë¡¢Ää»ß¤òºÆ³«¤¹¤ë¤Î¤¬
¤è¤ê´Êñ¤Ë¤Ç¤­¤ë¡£
.\"O .SH "RETURN VALUE"
.SH ÊÖ¤êÃÍ
.\"O On successfully sleeping for the requested interval,
.\"O .BR nanosleep ()
.\"O returns 0.
.\"O If the call is interrupted by a signal handler or encounters an error,
.\"O then it returns \-1, with
.\"O .I errno
.\"O set to indicate the error.
Í׵ᤵ¤ì¤¿´ü´Ö¤ÎÄä»ß¤ËÀ®¸ù¤·¤¿¾ì¹ç¡¢
.BR nanosleep ()
¤Ï 0 ¤òÊÖ¤¹¡£¸Æ¤Ó½Ð¤·¤¬¥·¥°¥Ê¥ë¥Ï¥ó¥É¥é¤Ë¤è¤ê³ä¤ê¹þ¤Þ¤ì¤¿¤ê¡¢
¥¨¥é¡¼¤¬È¯À¸¤·¤¿¾ì¹ç¤Ï¡¢\-1 ¤òÊÖ¤·¡¢
.I errno
¤Ë¥¨¥é¡¼ÆâÍƤò¼¨¤¹ÃͤòÀßÄꤹ¤ë¡£
.\"O .SH ERRORS
.SH ¥¨¥é¡¼
.TP
.B EFAULT
.\"O Problem with copying information from user space.
¥æ¡¼¥¶¶õ´Ö¤«¤é¤Î¾ðÊó¤Î¥³¥Ô¡¼¤ÇÌäÂ꤬¤¢¤Ã¤¿¡£
.TP
.B EINTR
.\"O The pause has been interrupted by a signal that was
.\"O delivered to the thread.
.\"O The remaining sleep time has been written
.\"O into \fI*rem\fP so that the thread can easily call
.\"O .BR nanosleep ()
.\"O again and continue with the pause.
¤½¤Î¥¹¥ì¥Ã¥É¤ËÇÛÁ÷¤µ¤ì¤¿¥·¥°¥Ê¥ë¤Ë¤è¤êÄä»ß¤¬ÃæÃǤµ¤ì¤¿¡£
¥¹¥ì¥Ã¥É¤¬´Êñ¤Ë
.BR nanosleep ()
¤òºÆ¤Ó¸Æ¤Ó½Ð¤·¤ÆÄä»ß¤ò³¤±¤ë¤³¤È¤¬¤Ç¤­¤ë¤è¤¦¤Ë¡¢
»Ä¤ê¤ÎÄä»ß»þ´Ö¤¬ \fI*rem\fP ¤Ë³ÊǼ¤µ¤ì¤ë¡£
.TP
.B EINVAL
.\"O The value in the
.\"O .I tv_nsec
.\"O field was not in the range 0 to 999999999 or
.\"O .I tv_sec
.\"O was negative.
.I tv_nsec
¥Õ¥£¡¼¥ë¥É¤ÎÃͤ¬ 0 ¤«¤é 999999999 ¤Þ¤Ç¤ÎÈϰϤˤʤ«¤Ã¤¿¤«¡¢
.I tv_sec
¤¬Éé¤Ç¤¢¤Ã¤¿¡£
.\"O .SH "CONFORMING TO"
.SH ½àµò
POSIX.1-2001.
.\"O .SH NOTES
.SH Ãí°Õ
.\"O If the interval specified in
.\"O .I req
.\"O is not an exact multiple of the granularity underlying clock (see
.\"O .BR time (7)),
.\"O then the interval will be rounded up to the next multiple.
.\"O Furthermore, after the sleep completes, there may still be a delay before
.\"O the CPU becomes free to once again execute the calling thread.
.I req
¤Ç»ØÄꤵ¤ì¤¿´ü´Ö¤¬¡¢ÆâÉô¤Ç»ÈÍѤµ¤ì¤ë¥¯¥í¥Ã¥¯¤ÎγÅÙ¤ÎÇÜ¿ô¤Ë¤Ê¤Ã¤Æ¤¤¤Ê¤¤
¾ì¹ç¡¢´ü´Ö¤Ï°ìÈֶᤤÇÜ¿ô¤ËÀÚ¤ê¾å¤²¤é¤ì¤ë¡£
¤Þ¤¿¡¢Ää»ß¤¬´°Î»¤·¤¿¸å¡¢CPU ¤¬¸Æ¤Ó½Ð¤·¸µ¤Î¥¹¥ì¥Ã¥É¤òºÆ¤Ó¼Â¹Ô¤Ç¤­¤ë¤è¤¦¤Ë
¤Ê¤ë¤Þ¤Ç¤Ë¤ÏÃٱ䤬Æþ¤ë¡£

.\"O The fact that
.\"O .BR nanosleep ()
.\"O sleeps for a relative interval can be problematic if the call
.\"O is repeatedly restarted after being interrupted by signals,
.\"O since the time between the interruptions and restarts of the call
.\"O will lead to drift in the time when the sleep finally completes.
.\"O This problem can be avoided by using
.\"O .BR clock_nanosleep (2)
.\"O with an absolute time value.
¥·¥°¥Ê¥ë¤Ë¤è¤ë³ä¤ê¹þ¤ß¸å¤Ë·«¤êÊÖ¤·ºÆ³«¤µ¤ì¤¿¾ì¹ç¡¢
.BR nanosleep ()
¤ÎÄä»ß¤¬ÁêÂÐŪ¤Ê´ü´Ö¤Ç¤¢¤ë¤³¤È¤ÏÌäÂê¤È¤Ê¤ë¤³¤È¤¬¤¢¤ë¡£
¤³¤ì¤Ï¡¢¸Æ¤Ó½Ð¤·¤Î³ä¤ê¹þ¤ß¤«¤éºÆ³«¤Þ¤Ç¤Î´Ö¤Î»þ´Ö¤¬¸¶°ø¤Ç
Ää»ß¤¬ºÇ½ªÅª¤Ë´°Î»¤·¤¿ºÝ¤Ë»þ´Ö¤Ë¤º¤ì¤¬È¯À¸¤¹¤ë¤«¤é¤Ç¤¢¤ë¡£
¤³¤ÎÌäÂê¤Ï¡¢ÀäÂлþ¹ï¤¬»ØÄê¤Ç¤­¤ë
.BR clock_nanosleep (2)
¤ò»È¤¦¤³¤È¤Ç²óÈò¤Ç¤­¤ë¡£

.\"O POSIX.1 specifies that
.\"O .BR nanosleep ()
.\"O should measure time against the
.\"O .B CLOCK_REALTIME
.\"O clock.
.\"O However, Linux measures the time using the
.\"O .B CLOCK_MONOTONIC
.\"O clock.
POSIX.1 ¤Ï¡¢
.BR nanosleep ()
¤Ï
.B CLOCK_REALTIME
¤ËÂФ·¤Æ»þ¹ï¤ò·×¬¤¹¤ë¤Ù¤­¤À¤Èµ¬Äꤷ¤Æ¤¤¤ë¡£
¤·¤«¤·¤Ê¤¬¤é¡¢Linux ¤Ï
.B CLOCK_MONOTONIC
¥¯¥í¥Ã¥¯¤òÍѤ¤¤Æ»þ¹ï¤ò·×¬¤·¤Æ¤¤¤ë¡£
.\" See also http://thread.gmane.org/gmane.linux.kernel/696854/
.\" Subject: nanosleep() uses CLOCK_MONOTONIC, should be CLOCK_REALTIME?
.\" Date: 2008-06-22 07:35:41 GMT
.\"O This probably does not matter, since the POSIX.1 specification for
.\"O .BR clock_settime (2)
.\"O says that discontinuous changes in
.\"O .B CLOCK_REALTIME
.\"O should not affect
.\"O .BR nanosleep ():
¤³¤Î¤³¤È¤Ï¤ª¤½¤é¤¯ÌäÂê¤Ë¤Ê¤é¤Ê¤¤¤À¤í¤¦¡£
¤Ê¤¼¤Ê¤é¡¢POSIX.1 ¤Î
.BR clock_settime (2)
¤Î»ÅÍͤˤϡ¢
.B CLOCK_REALTIME
¤ÎÉÔϢ³¤ÊÊѲ½¤Ï
.BR nanosleep ()
¤Ë±Æ¶Á¤¹¤Ù¤­¤Ç¤Ï¤Ê¤¤¡¢¤È½ñ¤«¤ì¤Æ¤¤¤ë¤«¤é¤Ç¤¢¤ë¡£
.RS
.PP
.\"O Setting the value of the
.\"O .B CLOCK_REALTIME
.\"O clock via
.\"O .BR clock_settime (2)
.\"O shall
.\"O have no effect on threads that are blocked waiting for a relative time
.\"O service based upon this clock, including the
.\"O .BR nanosleep ()
.\"O function; ...
.\"O Consequently, these time services shall expire when the requested relative
.\"O interval elapses, independently of the new or old value of the clock.
.BR clock_settime (2)
·Ðͳ¤Ç
.B CLOCK_REALTIME
¥¯¥í¥Ã¥¯¤ÎÃͤòÀßÄꤷ¤Æ¤â¡¢
.BR nanosleep ()
´Ø¿ô¤Ê¤É¤Î
.B CLOCK_REALTIME
¤Ë´ð¤Å¤¯¥µ¡¼¥Ó¥¹¤Ë¤è¤êÁêÂÐŪ¤Ê´ü´Ö¤À¤±¼Â¹Ô¤òÄä»ß¤¹¤ë¥¹¥ì¥Ã¥É¤Ë¤Ï±Æ¶Á¤Ï¤Ê¤¤¡£
·ë²Ì¤È¤·¤Æ¡¢¥¯¥í¥Ã¥¯Ãͤ¬¹¹¿·Á°¤«¸å¤«¤Ë´Ø¤ï¤é¤º¡¢Í׵ᤵ¤ì¤¿ÁêÂÐŪ¤Ê»þ´Ö¤¬
·Ð²á¤¹¤ë¤ÈËþλ¤¹¤ë¤³¤È¤Ë¤Ê¤ë¡£
.RE
.\"O .SS "Old behavior"
.SS °ÊÁ°¤ÎÆ°ºî
.\"O In order to support applications requiring much more precise pauses
.\"O (e.g., in order to control some time-critical hardware),
.\"O .BR nanosleep ()
.\"O would handle pauses of up to 2\ ms by busy waiting with microsecond
.\"O precision when called from a thread scheduled under a real-time policy
.\"O like
.\"O .B SCHED_FIFO
.\"O or
.\"O .BR SCHED_RR .
.\"O This special extension was removed in kernel 2.5.39,
.\"O hence is still present in
.\"O current 2.4 kernels, but not in 2.6 kernels.
(Î㤨¤Ð¡¢»þ´Ö¤¬½ÅÍפʰÕÌ£¤ò»ý¤Ä¥Ï¡¼¥É¥¦¥§¥¢¤òÀ©¸æ¤¹¤ë¾ì¹ç¤Ê¤É)
¤è¤êÀµ³Î¤ÊÄä»ß¤òɬÍפȤ¹¤ë¥¢¥×¥ê¥±¡¼¥·¥ç¥ó¤ËÂбþ¤¹¤ë¤¿¤á¤Ë¡¢
.BR nanosleep ()
¤Ï¡¢¥Þ¥¤¥¯¥íÉÃÀºÅ٤Υӥ¸¡¼¡¦¥¦¥§¥¤¥È¤òÍøÍѤ¹¤ë¤³¤È¤Ç¡¢
2\ ms °Ê²¼¤ÎÄä»ß¤ò¹Ô¤¦¤³¤È¤¬¤Ç¤­¤¿¡£
⤷¡¢¤³¤Îµ¡Ç½¤òÍøÍѤ¹¤ë¤Ë¤Ï¡¢¸Æ¤Ó½Ð¤·¸µ¤Î¥¹¥ì¥Ã¥É¤¬
.B SCHED_FIFO
¤ä
.B SCHED_RR
¤È¤¤¤Ã¤¿¥ê¥¢¥ë¥¿¥¤¥à¡¦¥Ý¥ê¥·¡¼¤Î¸µ¤Ç¥¹¥±¥¸¥å¡¼¥ê¥ó¥°¤µ¤ì¤Æ¤¤¤ë
ɬÍפ¬¤¢¤Ã¤¿¡£
¤³¤ÎÆÃÊ̤ʳÈÄ¥¤Ï¥«¡¼¥Í¥ë 2.5.39 ¤Çºï½ü¤µ¤ì¤¿¡£¤·¤¿¤¬¤Ã¤Æ¡¢
¸½ºß¤Î 2.4 ·ÏÎó¤Î¥«¡¼¥Í¥ë¤Ë¤Ï¤³¤Îµ¡Ç½¤¬Â¸ºß¤¹¤ë¤¬¡¢
2.6·ÏÎó¤Î¥«¡¼¥Í¥ë¤Ë¤Ï¤Ê¤¤¡£
.\"O .SH BUGS
.SH ¥Ð¥°
.\"O In Linux 2.4, if
.\"O .BR nanosleep ()
.\"O is stopped by a signal (e.g.,
.\"O .BR SIGTSTP ),
.\"O then the call fails with the error
.\"O .B EINTR
.\"O after the thread is resumed by a
.\"O .B SIGCONT
.\"O signal.
.\"O If the system call is subsequently restarted,
.\"O then the time that the thread spent in the stopped state is
.\"O \fInot\fP counted against the sleep interval.
Linux 2.4 ¤Ç¤Ï¡¢
.BR nanosleep ()
¤¬
.RB ( SIGTSTP
¤Ê¤É¤Î) ¥·¥°¥Ê¥ë¤Ë¤è¤êÄä»ß¤µ¤ì¤¿¾ì¹ç¡¢
.BR nanosleep ()
¤Î¸Æ¤Ó½Ð¤·¤Ï
.B SIGCONT
¥·¥°¥Ê¥ë¤Ë¤è¤ë¥¹¥ì¥Ã¥É¤ÎºÆ³«¸å¤Ë
.B EINTR
¥¨¥é¡¼¤Ç¼ºÇÔ¤¹¤ë¡£
¥·¥¹¥Æ¥à¥³¡¼¥ë¤¬¤³¤Î¸å¤ÇºÆ¥¹¥¿¡¼¥È¤µ¤ì¤¿¾ì¹ç¡¢
¥¹¥ì¥Ã¥É¤¬Ää»ß¾õÂ֤ˤ¢¤ë´Ö¤Ë·Ð²á¤·¤¿»þ´Ö¤Ï
Ää»ß´ü´Ö¤È¤·¤Æ¥«¥¦¥ó¥È¡Ö¤µ¤ì¤Ê¤¤¡×¡£
.\"O .SH "SEE ALSO"
.SH ´ØÏ¢¹àÌÜ
.BR clock_nanosleep (2),
.BR sched_setscheduler (2),
.BR timer_create (2),
.BR sleep (3),
.BR usleep (3),
.BR time (7)