.\" Copyright (C) 2008 Michael Kerrisk <mtk.manpages@gmail.com>
.\"
.\" This program is free software; 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.
.\"
.\" This program 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 program; if not, write to the Free Software
.\" Foundation, Inc., 59 Temple Place, Suite 330, Boston,
.\" MA  02111-1307  USA
.\"
.\" Japanese Version Copyright (c) 2008  Akihiro MOTOKI
.\"         all rights reserved.
.\" Translated 2008-11-19, Akihiro MOTOKI <amotoki@dd.iij4u.or.jp>, LDP v3.13
.\" 
.TH TIMERFD_CREATE 2 2009-02-11 Linux "Linux Programmer's Manual"
.SH ̾
timerfd_create, timerfd_settime, timerfd_gettime \-
եǥץͳΤ륿ޡ
.SH 
.nf
.B #include <sys/timerfd.h>
.sp
.BI "int timerfd_create(int " clockid ", int " flags );
.sp
.BI "int timerfd_settime(int " fd ", int " flags ,
.BI "                    const struct itimerspec *" new_value ,
.BI "                    struct itimerspec *" old_value );
.sp
.BI "int timerfd_gettime(int " fd ", struct itimerspec *" curr_value );
.fi
.SH 
ΥƥॳϡλΤեǥץͳ
ޡԤ
ϡ
.BR setitimer (2)

.BR timer_create (2)
ѤˡȤʤΤǤꡢΥեǥץ
.BR select (2),
.BR poll (2),
.BR epoll (7)
ǴƻǤȤ롣

ΥƥॳȤΤϡ줾
.BR timer_create (2),
.BR timer_settime (2),
.BR timer_gettime (2)
ȤΤƱͤǤ
.RB ( timer_getoverrun (2)
бΤϤʤʲ褦
εǽ
.BR read (2)
ˤ󶡤)
.\"
.SS timerfd_create()
.BR timerfd_create ()
ϿΥޡ֥ȤΥޡ򻲾Ȥե
ǥץ֤
.I clockid
ϡޡοĽ뤿ΥåꤹΤǡ
.B CLOCK_REALTIME

.B CLOCK_MONOTONIC
Τ줫ǤʤФʤʤ
.B CLOCK_REALTIME
ϥƥΤǻѤ륯åǡΥåѹǽǤ롣
.B CLOCK_MONOTONIC
ѹ뤳ȤΤʤåǡ(ƥμưǤѹʤɤ)
ƥ९åϢ³Ѳαƶʤ
Υåθߤͤ
.BR clock_gettime (2)
ȤäƼǤ롣

Linux 2.6.27 ʹߤǤϡ
ʲͤΤĤӥåñ̤ (OR) ǻꤹ뤳Ȥǡ
.BR timerfd_create ()
ο񤤤ѹ뤳ȤǤ롣
.TP 14
.B TFD_NONBLOCK
륪ץե뵭 (open file description) 
.B O_NONBLOCK
ե륹ơե饰򥻥åȤ롣
Υե饰ȤȤǡ
.B O_NONBLOCK
򥻥åȤ뤿
.BR fcntl (2)
ɲäǸƤӽФɬפʤʤ롣
.TP
.B TFD_CLOEXEC
եǥץФ
close-on-exec
.RB ( FD_CLOEXEC )
ե饰򥻥åȤ롣
Υե饰ΩͳˤĤƤϡ
.BR open (2)

.B O_CLOEXEC
ե饰򻲾ȤΤȡ
.PP
С 2.6.26  Linux Ǥϡ
.I flags
̤ѤǤꡢ0 ꤷʤФʤʤ
.SS timerfd_settime()
.BR timerfd_settime ()
ϡեǥץ
.I fd
ˤ껲Ȥ륿ޡ򳫻Ϥߤꤹ롣

.I new_value
ϡޡλ (expiration) νͤȴֳ (interval) 
ꤹ롣ΰǻѤƤ
.I itimerspec
¤Τˤ 2 ĤΥեɤꡢƥեɤ
.I timespec
ι¤ΤǤ롣
.in +4n
.nf

struct timespec {
    time_t tv_sec;                /* Seconds */
    long   tv_nsec;               /* Nanoseconds */
};

struct itimerspec {
    struct timespec it_interval;  /* Interval for periodic timer */
    struct timespec it_value;     /* Initial expiration */
};
.fi
.in
.PP
.I new_value.it_value
ϥޡλ֤νͤäȥʥäǻꤹ롣
.I new_value.it_value
ΥեɤΤʤȤ 0 ʳͤꤹȡ
ޡϤ롣
ξΥեɤ 0 ꤹȡޡߤ롣

.I new_value.it_interval
ϥޡΰܤλ˷֤ޡλֳ֤äȥʥäǻꤹ롣
.I new_value.it_interval
ΥեɤΤʤȤ 0 ʳͤꤹȡ
֤ޡͭˤʤ롣
ξΥեɤ 0 ꤷ硢ޡ
.I new_value.it_value
ǻꤵ줿ָˡλߤ롣

.I flags
ˤ 0 
.B TFD_TIMER_ABSTIME
ꤹ롣
0 л勵ޡ̣
.I new_value.it_interval
Ǥ
.I clockid
ǻꤵ줿åθߤͤŪʻꤹ롣
.B TFD_TIMER_ABSTIME
л勵ޡ̣
.I new_value.it_interval
Ǥ
.I clockid
ǻꤵ줿åлꤹ롣Ĥޤꡢ
åͤ
.I new_value.it_interval
ǻꤵ줿ã顢ޡλ롣

.I old_value
̤ơ
.BR timerfd_settime ()
ƤӽФǤΥޡݻ¤Τ֤롣

.BR timerfd_gettime ()
򻲾ȡ
.\"
.SS timerfd_gettime()
.BR timerfd_gettime ()
ϡեǥץ
.I fd
ǻȤ륿ޡθߤ꤬ä
.I itimerspec
¤Τ
.I curr_value
˳Ǽ֤

.I it_value
եɤϡޡλޤǤλĤ֤֤
ι¤ΤξΥեɤ 0 ǤСޡϸߤƤ롣
ޡ
.B TFD_TIMER_ABSTIME
ե饰ꤵ줿˴ؤ餺ΥեɤϾͤǼ롣

.I it_interval
եɤϡޡδֳ֤֤
ι¤ΤξΥեɤ 0 ǤСޡ
.I new_value.it_value
ǻꤵ줿ָ˰λߤ褦ꤵƤ롣
.SS ޡեǥץФ
.BR timerfd_create ()
֤եǥץϰʲ򥵥ݡȤƤ롣
.TP
.BR read (2)
.BR timerfd_settime ()
Ȥäƥޡ꤬Ǹѹưʹߡޤ
.BR read (2)
θƤӽФ˺ǸưʹߤˡޡλʾȯƤС
.BR read (2)
Ϥ줿Хåեˡޡλ򼨤 8 ХȤ unsigned 
.RI ( uint64_t )
֤
(֤ͤϥۥȥХȥĤޤꤽΥۥȥޥˤ
̾ΥХȥǤ)
.IP
.BR read (2)
ԤäǥޡλȯƤʤС
.BR read (2)
 (block) 롢⤷ϥեǥץ
 (non-blocking) ꤵƤϥ顼
.B EAGAIN
ǼԤ (ߥ⡼ɤˤˤϡ
.BR fcntl (2)

.B F_SETFL
̿
.B O_NONBLOCK
ե饰򥻥åȤ)
.IP
Ϥ줿ХåեΥ 8 Х̤ξ硢
.BR read (2)
ϥ顼
.B EINVAL
ǼԤ롣
.TP
.BR poll "(2), " select "(2) (Ʊͤ)"
İʾΥޡλȯƤС
եǥץɤ߽ФǽȤʤ
.RB ( select (2)

.I readfds

.BR poll (2)

.B POLLIN
ե饰)
.IP
Υեǥץϡ¾Υեǥץ¿ API Ǥ
.BR pselect (2),
.BR ppoll (2),
.BR epoll (7)
⥵ݡȤƤ롣
.TP
.BR close (2)
եǥץʹߤɬפʤʤäݤˤϡ٤Ǥ롣
Ʊ timer ֥Ȥ˴Ϣդ줿եǥץ
ȡΥޡϲ졢
Υ֥Ѥλ񸻤ͥˤ롣
.\"
.SS fork(2) Ǥΰ
.BR fork (2)
Ԥȡҥץ
.BR timerfd_create ()
ˤ줿եǥץΥԡ
Ѿ롣Υեǥץϡƥץб
եǥץƱޡ֥Ȥ򻲾ȤƤꡢ
ҥץ
.BR read (2)
ǤƱޡλ˴ؤ֤롣
.\"
.SS execve(2) Ǥΰ
.BR execve (2)

.BR timerfd_create ()
ˤ줿եǥץݻ졢
ޡϤƤˤϥޡλȯ³롣
.SH ֤
ȡ
.BR timerfd_create ()
Ͽեǥץ֤
顼ξ硢\-1 ֤
.I errno
˥顼򼨤ͤꤹ롣

.BR timerfd_settime ()

.BR timerfd_gettime ()
 0 ֤
顼ξ硢\-1 ֤
.I errno
˥顼򼨤ͤꤹ롣
.SH 顼
.BR timerfd_create ()
ϰʲΥ顼ǼԤǽ롣
.TP
.B EINVAL
.I clockid

.B CLOCK_MONOTONIC
Ǥ
.B CLOCK_REALTIME
Ǥʤ
.TP
.B EINVAL
.I flags
̵Ǥ롣⤷ϡLinux 2.6.26 ξ
.I flags
 0 ʳǤ롣
.TP
.B EMFILE
ץѤߤΥեǥץοץξ¤
ãƤ
.TP
.B ENFILE
ץѤߤΥեƥΤξ¤ãƤ
.TP
.B ENODEV
(ͥ) ̵̾ inode ǥХޥȤǤʤä
.TP
.B ENOMEM
ޡΤ˽ʬʥ꤬ͥʤä
.PP
.BR timerfd_settime ()

.BR timerfd_gettime ()
ϰʲΥ顼ǼԤǽ롣
.TP
.B EBADF
.I fd
ͭʥեǥץǤʤ
.TP
.B EFAULT
.IR new_value ,
.IR old_value ,
.I curr_value
ͭʥݥ󥿤ǤϤʤ
.TP
.B EINVAL
.I fd
ͭ timerfd եǥץǤʤ
.I new_value
Ŭڤ˽Ƥʤ
.RI ( tv_nsec
ΰĤ 0  999,999,999 ޤǤϰϤäƤʤ)
.SH С
Υƥॳϥͥ 2.6.25 ʹߤ Linux ѲǽǤ롣
饤֥¦ΥݡȤϥС 2.8 ʹߤ glibc 󶡤Ƥ롣
.SH 
Υƥॳ Linux ͭǤ롣
.SH 
ʲΥץϡޡοĽ˥ΤǤ롣
ΥץϺ 3 ĤΥޥɥ饤ꡢ
Ǥϥޡλ֤ν (ÿñ) 
Ǥϥޡδֳ (ÿñ) 
軰Ǥϥޡλץबλ뤫ꤹ롣
軰ϾάǽǤ롣

ʲΥΥåϤΥץλ򼨤ΤǤ롣
.in +4n
.nf

.RB "$" " a.out 3 1 100"
0.000: timer started
3.000: read: 1; total=1
4.000: read: 1; total=2
.BR "^Z " "                 # type control-Z to suspend the program"
[1]+  Stopped                 ./timerfd3_demo 3 1 100
.RB "$ " "fg" "                # Resume execution after a few seconds"
a.out 3 1 100
9.660: read: 5; total=7
10.000: read: 1; total=8
11.000: read: 1; total=9
.BR "^C " "                 # type control-C to suspend the program"
.fi
.in
.SS ץΥ
\&
.nf
.\" The commented out code here is what we currently need until
.\" the required stuff is in glibc
.\"
.\"
.\"/* Link with -lrt */
.\"#define _GNU_SOURCE
.\"#include <sys/syscall.h>
.\"#include <unistd.h>
.\"#include <time.h>
.\"#if defined(__i386__)
.\"#define __NR_timerfd_create 322
.\"#define __NR_timerfd_settime 325
.\"#define __NR_timerfd_gettime 326
.\"#endif
.\"
.\"static int
.\"timerfd_create(int clockid, int flags)
.\"{
.\"    return syscall(__NR_timerfd_create, clockid, flags);
.\"}
.\"
.\"static int
.\"timerfd_settime(int fd, int flags, struct itimerspec *new_value,
.\"        struct itimerspec *curr_value)
.\"{
.\"    return syscall(__NR_timerfd_settime, fd, flags, new_value,
.\"                   curr_value);
.\"}
.\"
.\"static int
.\"timerfd_gettime(int fd, struct itimerspec *curr_value)
.\"{
.\"    return syscall(__NR_timerfd_gettime, fd, curr_value);
.\"}
.\"
.\"#define TFD_TIMER_ABSTIME (1 << 0)
.\"
.\"////////////////////////////////////////////////////////////
#include <sys/timerfd.h>
#include <time.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <stdint.h>        /* Definition of uint64_t */

#define handle_error(msg) \\
        do { perror(msg); exit(EXIT_FAILURE); } while (0)

static void
print_elapsed_time(void)
{
    static struct timespec start;
    struct timespec curr;
    static int first_call = 1;
    int secs, nsecs;

    if (first_call) {
        first_call = 0;
        if (clock_gettime(CLOCK_MONOTONIC, &start) == \-1)
            handle_error("clock_gettime");
    }

    if (clock_gettime(CLOCK_MONOTONIC, &curr) == \-1)
        handle_error("clock_gettime");

    secs = curr.tv_sec \- start.tv_sec;
    nsecs = curr.tv_nsec \- start.tv_nsec;
    if (nsecs < 0) {
        secs\-\-;
        nsecs += 1000000000;
    }
    printf("%d.%03d: ", secs, (nsecs + 500000) / 1000000);
}

int
main(int argc, char *argv[])
{
    struct itimerspec new_value;
    int max_exp, fd;
    struct timespec now;
    uint64_t exp, tot_exp;
    ssize_t s;

    if ((argc != 2) && (argc != 4)) {
        fprintf(stderr, "%s init\-secs [interval\-secs max\-exp]\\n",
                argv[0]);
        exit(EXIT_FAILURE);
    }

    if (clock_gettime(CLOCK_REALTIME, &now) == \-1)
        handle_error("clock_gettime");

    /* Create a CLOCK_REALTIME absolute timer with initial
       expiration and interval as specified in command line */

    new_value.it_value.tv_sec = now.tv_sec + atoi(argv[1]);
    new_value.it_value.tv_nsec = now.tv_nsec;
    if (argc == 2) {
        new_value.it_interval.tv_sec = 0;
        max_exp = 1;
    } else {
        new_value.it_interval.tv_sec = atoi(argv[2]);
        max_exp = atoi(argv[3]);
    }
    new_value.it_interval.tv_nsec = 0;

    fd = timerfd_create(CLOCK_REALTIME, 0);
    if (fd == \-1)
        handle_error("timerfd_create");

    if (timerfd_settime(fd, TFD_TIMER_ABSTIME, &new_value, NULL) == \-1)
        handle_error("timerfd_settime");

    print_elapsed_time();
    printf("timer started\\n");

    for (tot_exp = 0; tot_exp < max_exp;) {
        s = read(fd, &exp, sizeof(uint64_t));
        if (s != sizeof(uint64_t))
            handle_error("read");

        tot_exp += exp;
        print_elapsed_time();
        printf("read: %llu; total=%llu\\n",
                (unsigned long long) exp,
                (unsigned long long) tot_exp);
    }

    exit(EXIT_SUCCESS);
}
.fi
.SH Х
ߤΤȤ
.\" 2.6.29
.BR timerfd_create ()
бƤ clockid μ
.BR timer_create (2)
⾯ʤ
.SH Ϣ
.BR eventfd (2),
.BR poll (2),
.BR read (2),
.BR select (2),
.BR setitimer (2),
.BR signalfd (2),
.BR timer_create (2),
.BR timer_gettime (2),
.BR timer_settime (2),
.BR epoll (7),
.BR time (7)