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sem_wait

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sem_wait, sem_timedwait, sem_trywait - ¥»¥Þ¥Õ¥©¤ò¥í¥Ã¥¯¤¹¤ë

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#include <semaphore.h>



int sem_wait(sem_t *sem);

int sem_trywait(sem_t *sem);



#define _XOPEN_SOURCE 600

#include <semaphore.h>



int sem_timedwait(sem_t *sem, const struct timespec *abs_timeout);

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sem_timedwait() ¤Ï sem_wait() ¤ÈƱ¤¸¤À¤¬¡¢¥»¥Þ¥Õ¥©Ãͤθº»»¤ò¤¹¤°¤Ë¼Â¹Ô¤Ç¤­¤Ê¤«¤Ã¤¿¾ì¹ç¤Ë ´Ø¿ô¸Æ¤Ó½Ð¤·¤¬Ää»ß¤¹¤ë»þ´Ö¤Î¾å¸Â¤ò abs_timeout ¤Ç»ØÄꤹ¤ëÅÀ¤¬°Û¤Ê¤ë¡£ abs_timeout °ú¤­¿ô¤Ï¡¢¥¿¥¤¥à¥¢¥¦¥È»þ¹ï¤ò»ØÄꤹ¤ë¹½Â¤ÂΤؤΥݥ¤¥ó¥¿¤Ç¤¢¤ë¡£ ¤³¤Î¹½Â¤ÂΤˤϡ¢¥¿¥¤¥à¥¢¥¦¥È»þ¹ï¤ò»þ¹ïµª¸µ (Epoch; 1970 ǯ 1 ·î 1 Æü 00:00:00) ¤«¤é¤Î·Ð²á»þ´Ö (ÉáܥʥÎÉÃ) ¤Ç»ØÄꤹ¤ë¡£ ¹½Â¤ÂΤϰʲ¼¤Î¤è¤¦¤ËÄêµÁ¤µ¤ì¤Æ¤¤¤ë:

struct timespec {

    time_t tv_sec;      /* Seconds */

    long   tv_nsec;     /* Nanoseconds [0 .. 999999999] */

};

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EINTR

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EINVAL

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EAGAIN

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EINVAL

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ETIMEDOUT

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$ ./a.out 2 3

About to call sem_timedwait()

sem_post() from handler

sem_getvalue() from handler; value = 1

sem_timedwait() succeeded

$ ./a.out 2 1

About to call sem_timedwait()

sem_timedwait() timed out

¥×¥í¥°¥é¥à¤Î¥½¡¼¥¹¥³¡¼¥É¤Ï°Ê²¼¤ÎÄ̤ê¤Ç¤¢¤ë:

#include <unistd.h>

#include <stdio.h>

#include <stdlib.h>

#include <semaphore.h>

#include <time.h>

#include <assert.h>

#include <errno.h>

#include <signal.h>



#define die(msg) { perror(msg); exit(EXIT_FAILURE); }



sem_t sem;



static void

handler(int sig)

{

    int sval;



    printf("sem_post() from handler\n");

    if (sem_post(&sem) == -1)

        die("sem_post");



    if (sem_getvalue(&sem, &sval) == -1)

        die("sem_getvalue");

    printf("sem_getvalue() from handler; value = %d\n", sval);

} /* handler */



int

main(int argc, char *argv[])

{

    struct sigaction sa;

    struct timespec ts;

    int s;



    assert(argc == 3);  /* Usage: ./a.out alarm-secs wait-secs */



    if (sem_init(&sem, 0, 0) == -1)

        die("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)

        die("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)

        die("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 when interrupted by handler */



    /* Check what happened */



    if (s == -1) {

        if (errno == ETIMEDOUT)

            printf("sem_timedwait() timed out\n");

        else

            die("sem_timedwait");

    } else

        printf("sem_timedwait() succeeded\n");



    exit(EXIT_SUCCESS);

}

´ØÏ¢¹àÌÜ

sem_getvalue(3), sem_post(3), feature_test_macros(7), sem_overview(7)