'\" t
.\" Hey Emacs! This file is -*- nroff -*- source.
.\"
.\" Copyright (C) 2006 Michael Kerrisk <mtk.manpages@gmail.com>
.\"
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.\" manual provided the copyright notice and this permission notice are
.\" preserved on all copies.
.\"
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.\" manual under the conditions for verbatim copying, provided that the
.\" entire resulting derived work is distributed under the terms of a
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.\" manual page may be incorrect or out-of-date.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
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.\" professionally.
.\"
.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
.\"
.\" Japanese Version Copyright (c) 2006 Akihiro MOTOKI all rights reserved.
.\" Translated 2006-04-18, Akihiro MOTOKI <amotoki@dd.iij4u.or.jp>
.\"
.TH SEM_WAIT 3 2009-02-09 "Linux" "Linux Programmer's Manual"
.SH ̾
sem_wait, sem_timedwait, sem_trywait \- ޥեå
.SH 
.nf
.B #include <semaphore.h>
.sp
.BI "int sem_wait(sem_t *" sem );
.sp
.BI "int sem_trywait(sem_t *" sem );
.sp
.BI "int sem_timedwait(sem_t *" sem ", const struct timespec *" abs_timeout );
.fi
.sp
.sp
\fI\-lrt\fP ޤ \fI\-pthread\fP ǥ󥯤롣
.in -4n
glibc εǽޥ׷
.RB ( feature_test_macros (7)
):
.in
.sp
.BR sem_timedwait ():
_POSIX_C_SOURCE\ >=\ 200112L || _XOPEN_SOURCE\ >=\ 600
.SH 
.BR sem_wait ()

.I sem
ؤޥեͤ 1 餹 (å)
ޥեͤ 0 礭硢¹Ԥ졢ؿľ롣
ޥեθͤ 0 ξˤϡ¹ԤǤ褦ˤʤ
(Ĥޤꡢޥեͤ 0 礭ͤˤʤ) ޤǡ⤷
ʥϥɥˤäƸƤӽФǤޤǡ
ؿƤӽФ (block) 롣

.BR sem_trywait ()

.BR sem_wait ()
Ʊޥեͤθ򤹤˼¹ԤǤʤäˡ
 (block) ΤǤϤʤ顼
.RI ( errno

.B EAGAIN
åȤ) ۤʤ롣

.BR sem_timedwait ()

.BR sem_wait ()
Ʊޥեͤθ򤹤˼¹ԤǤʤä
ؿƤӽФߤ֤ξ¤
.I abs_timeout
ǻꤹۤʤ롣
.I abs_timeout
ϡॢȻꤹ빽¤ΤؤΥݥ󥿤Ǥ롣
ι¤ΤˤϡॢȻﵪ (Epoch; 1970 ǯ 1  1 
00:00:00) ηв (áܥʥ) ǻꤹ롣
¤ΤϰʲΤ褦Ƥ:

.nf
.in +4n
struct timespec {
    time_t tv_sec;      /* Seconds */
    long   tv_nsec;     /* Nanoseconds [0 .. 999999999] */
};
.in
.fi
.PP
ؿƤӽФǤǤ˥ॢȤ˻ꤷ郎᤮Ƥꡢ
ĥޥե򤹤˥åǤʤäϡ
.BR sem_timedwait ()
ϥॢȥ顼
.RI ( errno

.B ETIMEDOUT
åȤ) ǼԤ롣

ޥե˼¹ԤǤȤϡ
.I abs_timeout
ɤͤǤäƤ
.BR sem_timedwait ()
Ԥ뤳ȤϷ褷Ƥʤˤȡξˤ
.I abs_timeout
θϹԤʤ
.SH ֤
ȡδؿ 0 ֤
顼ξ硢ޥեͤѹˡ\-1 ֤
.I errno
˥顼򼨤ͤ򥻥åȤ롣
.SH 顼
.TP
.B EINTR
ƤӽФϥʥϥɥˤǤ줿
.BR signal (7)
ȡ
.TP
.B EINVAL
.I sem
ͭʥޥեǤʤ
.PP
.BR sem_trywait ()
ξˤϡ嵭˲äưʲΥ顼ⵯ롣
.TP
.B EAGAIN
 (block) ˥åλǤʤä (Ĥޤꡢ
ޥեθߤͤ 0 Ǥä)
.PP
.BR sem_timedwait ()
ξ硢ʲΥ顼ⵯ롣
.TP
.B EINVAL
.I abs_timeout.tv_nsecs
ͤ 0 ̤⤷ 1,000,000,000 ʾǤ롣
.TP
.B ETIMEDOUT
ޥեΥå˻ڤȤʤä
.\" POSIX.1-2001 Ǥϥ顼Ȥ EDEADLK ѰդƤ롣
.\" ϥǥåɥå򸡽ФȤ򼨤Τ
.\" Linux ȯ뤳ȤϤʤ(?)
POSIX.1-2001.
.SH 
ʥϥɥϡ
.BR sigaction (2)

.B SA_RESTART
ե饰ѤƤ뤫ɤ˴ؤ餺δؿθƤӽФ
ߤƤ硢ʥϥɥˤǤ롣
.\" sem_wait() ¾ΤۤȤɤμǤϾǤ뤬
.\" FreeBSD 5.4 Ǥ SA_RESTART ꤷƤȼ¹ԤƳ롣
.SH 
.PP
ʲ˼ (äȤ) ץ̾ʤޥեԤ
ץϥޥɥ饤 2 ļ롣
ǽΰˤϡ
.B SIGALRM
ʥ뤿Υ顼ॿޡ˻Ȥͤ
ñ̤ǻꤹ롣Υʥϥɥϡ
.I main()

.BR sem_timedwait ()
ȤäԤäƤ륻ޥե
.BR sem_post (3)
ȤäƲû롣
2ܤΰˤϡ
.BR sem_timedwait ()
ϤॢȤޤǤλ֤ñ̤ǻꤹ롣

.in +4n
.nf
.RB "$" " ./a.out 2 3"
About to call sem_timedwait()
sem_post() from handler
sem_getvalue() from handler; value = 1
sem_timedwait() succeeded
.RB "$" " ./a.out 2 1"
About to call sem_timedwait()
sem_timedwait() timed out
.fi
.in
.SS ץΥ
\&
.nf
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <semaphore.h>
#include <time.h>
#include <assert.h>
#include <errno.h>
#include <signal.h>

sem_t sem;

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

static void
handler(int sig)
{
    write(STDOUT_FILENO, "sem_post() from handler\\n", 24);
    if (sem_post(&sem) == \-1) {
        write(STDERR_FILENO, "sem_post() failed\\n", 18);
        _exit(EXIT_FAILURE);
    }
}

int
main(int argc, char *argv[])
{
    struct sigaction sa;
    struct timespec ts;
    int s;

    if (argc != 3) {
        fprintf(stderr, "Usage: %s <alarm\-secs> <wait\-secs>\\n",
                argv[0]);
        exit(EXIT_FAILURE);
    }

    if (sem_init(&sem, 0, 0) == \-1)
        handle_error("sem_init");

    /* Establish SIGALRM handler; set alarm timer using argv[1] */

    sa.sa_handler = handler;
    sigemptyset(&sa.sa_mask);
    sa.sa_flags = 0;
    if (sigaction(SIGALRM, &sa, NULL) == \-1)
        handle_error("sigaction");

    alarm(atoi(argv[1]));

    /* Calculate relative interval as current time plus
       number of seconds given argv[2] */

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

    ts.tv_sec += atoi(argv[2]);

    printf("main() about to call sem_timedwait()\\n");
    while ((s = sem_timedwait(&sem, &ts)) == \-1 && errno == EINTR)
        continue;       /* Restart if interrupted by handler */

    /* Check what happened */

    if (s == \-1) {
        if (errno == ETIMEDOUT)
            printf("sem_timedwait() timed out\\n");
        else
            perror("sem_timedwait");
    } else
        printf("sem_timedwait() succeeded\\n");

    exit((s == 0) ? EXIT_SUCCESS : EXIT_FAILURE);
}
.fi
.SH Ϣ
.BR clock_gettime (2),
.BR sem_getvalue (3),
.BR sem_post (3),
.BR sem_overview (7),
.BR time (7)