Linux Certif

Toute la documentation sur la certification Linux LPI

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wait, waitpid, waitid - ¥×¥í¥»¥¹¤Î¾õÂÖÊѲ½¤òÂÔ¤Ä

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#include <sys/types.h>
#include <sys/wait.h>

pid_t wait(int *status);
pid_t waitpid(pid_t pid, int *status, int options);
int waitid(idtype_t idtype, id_t id, siginfo_t *infop, int options);

ÀâÌÀ

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wait() ¤È waitpid()

wait() ¥·¥¹¥Æ¥à¥³¡¼¥ë¤Ï¡¢»Ò¥×¥í¥»¥¹¤Î¤¤¤º¤ì¤«¤¬½ªÎ»¤¹¤ë¤Þ¤Ç¥«¥ì¥ó¥È¡¦¥×¥í¥»¥¹ ¤Î¼Â¹Ô¤ò°ì»þÄä»ß¤¹¤ë¡£ °Ê²¼¤ÎÆó¤Ä¤Î¸Æ¤Ó½Ð¤·¤ÏÅù²Á¤Ç¤¢¤ë:

    wait(&status);



    waitpid(-1, &status, 0);

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pid ¤Ë»ØÄê¤Ç¤­¤ëÃͤϰʲ¼¤ÎÄ̤ê:

< -1

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0

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> 0

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options ¤ÎÃͤϼ¡¤ÎÄê¿ô¤Î 0 ¸Ä°Ê¾å¤ÎÏÀÍýϤǤ¢¤ë:

WNOHANG

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WUNTRACED

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WCONTINUED

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(Linux ÀìÍÑ¥ª¥×¥·¥ç¥ó¤Ë¤Ä¤¤¤Æ¤Ï¸å½Ò¤¹¤ë)

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status ¤¬ NULL ¤Ç¤Ê¤±¤ì¤Ð¡¢ wait() ¤ä waitpid() ¤Ï status ¤Ç»Ø¤¹ int ¤Ë¾õÂÖ¾ðÊó¤ò³ÊǼ¤¹¤ë¡£ ¤³¤ÎÀ°¿ô¤Ï°Ê²¼¤Î¥Þ¥¯¥í¤ò»È¤Ã¤Æ¸¡ºº¤Ç¤­¤ë¡£ (¤³¤ì¤é¤Î¥Þ¥¯¥í¤Î°ú¤­¿ô¤Ë¤Ï¡¢ wait() ¤ä waitpid() ¤¬½ñ¤­¹þ¤ó¤ÀÀ°¿ô¤½¤Î¤â¤Î¤ò»ØÄꤹ¤ë¡£¥Ý¥¤¥ó¥¿¤Ç¤Ï¤Ê¤¤!)

WIFEXITED(status)

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WEXITSTATUS(status)

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WIFSIGNALED(status)

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WTERMSIG(status)

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WCOREDUMP(status)

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WIFSTOPPED(status)

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WSTOPSIG(status)

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WIFCONTINUED(status)

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waitid()

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°ú¤­¿ô idtype ¤È id ¤Ç¤É¤Î»Ò¥×¥í¥»¥¹¤òÂԤĤ«¤òÁªÂò¤¹¤ë:

idtype == P_PID

¥×¥í¥»¥¹ID ¤¬ id ¤È°ìÃפ¹¤ë»Ò¥×¥í¥»¥¹¤òÂԤġ£

idtype == P_PGID

¥×¥í¥»¥¹¥°¥ë¡¼¥×ID ¤¬ id ¤È°ìÃפ¹¤ë»Ò¥×¥í¥»¥¹¤òÂԤġ£

idtype == P_ALL

»Ò¥×¥í¥»¥¹Á´Éô¤òÂоݤËÂԤġ£ id ¤Ï̵»ë¤µ¤ì¤ë¡£

»Ò¥×¥í¥»¥¹¤Î¤É¤Î¾õÂÖÊѲ½¤òÂԤĤ«¤Ï°Ê²¼¤Î¥Õ¥é¥°¤Ç»ØÄꤹ¤ë (options ¤Ë¤Ï 1¸Ä°Ê¾å¤Î¥Õ¥é¥°¤ÎÏÀÍýϤò¤È¤Ã¤Æ»ØÄꤹ¤ë):

WEXITED

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WSTOPPED

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WCONTINUED

(Ää»ß¤·¤Æ¤¤¤¿) »Ò¥×¥í¥»¥¹¤¬ SIGCONT ¤¬ÇÛÁ÷¤µ¤ì¤ÆºÆ³«¤¹¤ë¤Î¤òÂԤġ£

¤µ¤é¤Ë°Ê²¼¤Î¥Õ¥é¥°¤òÏÀÍýϤηÁ¤Ç options ¤Ë»ØÄê¤Ç¤­¤ë:

WNOHANG

waitpid() ¤ÈƱÍÍ¡£

WNOWAIT

waitable ¾õÂÖ¤Î¥×¥í¥»¥¹¤ò¤½¤Î¤Þ¤Þ¤Ë¤¹¤ë¡£¤³¤Î¸å¤Ç wait ¥³¡¼¥ë¤ò »È¤Ã¤Æ¡¢Æ±¤¸»Ò¥×¥í¥»¥¹¤Î¾õÂÖ¾ðÊó¤ò¤â¤¦°ìÅÙ¼èÆÀ¤¹¤ë¤³¤È¤¬¤Ç¤­¤ë¡£

À®¸ù¤·¤¿¾ì¹ç¤Ë¤Ï¡¢ waitid() ¤Ï infop ¤¬»Ø¤¹ siginfo_t ¹½Â¤ÂΤΰʲ¼¤Î¥Õ¥£¡¼¥ë¥É¤òÀßÄꤹ¤ë:

si_pid

»Ò¥×¥í¥»¥¹¤Î¥×¥í¥»¥¹ID¡£

si_uid

»Ò¥×¥í¥»¥¹¤Î¼Â¥æ¡¼¥¶ID (¤³¤Î¥Õ¥£¡¼¥ë¥É¤Ï¾¤Î¤Û¤È¤ó¤É¤Î¼ÂÁõ¤Ç¤ÏÀßÄꤵ¤ì¤Ê¤¤)¡£

si_signo

¾ï¤Ë SIGCHLD ¤¬ÀßÄꤵ¤ì¤ë¡£

si_status

_exit(2) (¤« exit(3)) ¤Ë»ØÄꤵ¤ì¤¿»Ò¥×¥í¥»¥¹¤Î½ªÎ»¥¹¥Æ¡¼¥¿¥¹¡¢¤â¤·¤¯¤Ï »Ò¥×¥í¥»¥¹¤Î½ªÎ»¡¢Ää»ß¡¢ºÆ³«¤Î¸¶°ø¤È¤Ê¤Ã¤¿¥·¥°¥Ê¥ë¤¬ÀßÄꤵ¤ì¤ë¡£ ¤³¤Î¥Õ¥£¡¼¥ë¥É¤ò¤É¤¦²ò¼á¤¹¤ë¤«¤Ï¡¢ si_code ¥Õ¥£¡¼¥ë¥É¤ò»²¾È¤·¤Æ·è¤á¤ë¤³¤È¤¬¤Ç¤­¤ë¡£

si_code

°Ê²¼¤Î¤¤¤º¤ì¤«¤¬ÀßÄꤵ¤ì¤ë: CLD_EXITED (»Ò¥×¥í¥»¥¹¤¬ _exit(2) ¤ò¸Æ¤Ó½Ð¤·¤¿); CLD_KILLED (¥·¥°¥Ê¥ë¤Ë¤è¤ê»Ò¥×¥í¥»¥¹¤¬ kill ¤µ¤ì¤¿); CLD_STOPPED (¥·¥°¥Ê¥ë¤Ë¤è¤ê»Ò¥×¥í¥»¥¹¤¬Ää»ß¤·¤¿); CLD_CONTINUED (SIGCONT ¤Ë¤è¤ê»Ò¥×¥í¥»¥¹¤¬ºÆ³«¤µ¤ì¤¿)¡£

WNOHANG ¤¬ options ¤Ë»ØÄꤵ¤ì¤Æ¤¤¤Æ¡¢ waitable ¾õÂÖ¤Î»Ò¥×¥í¥»¥¹¤¬¤Ê¤«¤Ã¤¿¾ì¹ç¤Ë¤Ï¡¢ waitid() ¤Ï¤¹¤°¤Ë 0 ¤òÊÖ¤¹¡£¤³¤Î¤È¤­¡¢ infop ¤¬»Ø¤¹ siginfo_t ¹½Â¤ÂΤÎÆâÍƤÏÉÔÄê¤Ç¤¢¤ë¡£ ¤³¤Î¾ì¹ç¤ò waitable ¾õÂÖ¤Î»Ò¥×¥í¥»¥¹¤¬¤¢¤Ã¤¿¾ì¹ç¤È¶èÊ̤¹¤ë¤Ë¤Ï¡¢ waitid() ¤ò¸Æ¤Ó½Ð¤¹Á°¤Ë si_pid ¤ò 0 ¤Ë¤·¤Æ¤ª¤­¡¢¥³¡¼¥ë¤¬Éüµ¢¤·¤¿¸å¤Ç¤³¤Î¥Õ¥£¡¼¥ë¥É¤¬ 0 °Ê³°¤ÎÃͤ«¤É¤¦¤« ¤ò¥Á¥§¥Ã¥¯¤¹¤ì¤Ð¤è¤¤¡£

ÊÖ¤êÃÍ

wait(): À®¸ù¤¹¤ë¤È¡¢½ªÎ»¤·¤¿»Ò¥×¥í¥»¥¹¤Î¥×¥í¥»¥¹ID ¤òÊÖ¤¹¡£ ¥¨¥é¡¼¤Î¾ì¹ç -1 ¤òÊÖ¤¹¡£

waitpid(): À®¸ù¤¹¤ë¤È¡¢¾õÂÖ¤¬ÊѲ½¤·¤¿»Ò¥×¥í¥»¥¹¤Î¥×¥í¥»¥¹ID ¤òÊÖ¤¹¡£ ¥¨¥é¡¼¤Î¾ì¹ç -1 ¤òÊÖ¤¹¡£ WNOHANG ¤¬»ØÄꤵ¤ì¤Æ¤¤¤Æ¡¢ pid ¤Ç»Ø¼¨¤µ¤ì¤¿»Ò¥×¥í¥»¥¹¤Ç¾õÂÖÊѲ½¤¬µ¯¤³¤Ã¤Æ¤¤¤Ê¤«¤Ã¤¿¾ì¹ç¤Ï¡¢ 0 ¤òÊÖ¤¹¡£

waitid(): À®¸ù¤¹¤ë¤È 0 ¤òÊÖ¤¹¡£ WNOHANG ¤¬»ØÄꤵ¤ì¤Æ¤¤¤Æ¡¢ pid ¤Ç»Ø¼¨¤µ¤ì¤¿»Ò¥×¥í¥»¥¹¤Ç¾õÂÖÊѲ½¤¬µ¯¤³¤Ã¤Æ¤¤¤Ê¤«¤Ã¤¿¾ì¹ç¤Ë¤â 0 ¤òÊÖ¤¹¡£ ¥¨¥é¡¼¤Î¾ì¹ç -1 ¤òÊÖ¤¹¡£

¥¨¥é¡¼¤Î¾ì¹ç¡¢¤³¤ì¤é¤Î¥·¥¹¥Æ¥à¥³¡¼¥ë¤Ï¤¤¤º¤ì¤â errno ¤ËŬÀÚ¤ÊÃͤòÀßÄꤹ¤ë¡£

¥¨¥é¡¼

ECHILD

(wait() ¤Î¾ì¹ç) ¸Æ¤Ó½Ð¤·¸µ¥×¥í¥»¥¹¤Ë¤Ï¡¢wait ¤ò¹Ô¤Ã¤Æ¤¤¤Ê¤¤»Ò¥×¥í¥»¥¹¤Ï¤Ê¤¤¡£

ECHILD

(waitpid() ¤« waitid() ¤Î¾ì¹ç) pid (waitpid()) ¤« idtype ¤È id (waitid()) ¤Ç»ØÄꤷ¤¿¥×¥í¥»¥¹¤¬Â¸ºß¤·¤Ê¤¤¤«¡¢¸Æ¤Ó½Ð¤·¸µ¥×¥í¥»¥¹¤Î»Ò¥×¥í¥»¥¹¤Ç¤Ê¤¤ (SIGCHLD ¤ÎÆ°ºî¤Ë SIG_IGN ¤òÀßÄꤷ¤¿¾ì¹ç¤Ë¤Ï¡¢ ¼«Ê¬¼«¿È¤Î»Ò¥×¥í¥»¥¹¤Ç¤âµ¯¤³¤ê¤¦¤ë¡£ ¥¹¥ì¥Ã¥É¤Ë´Ø¤·¤Æ¤Ï¡ÖLinux ¤Ç¤ÎÃí°Õ¡×¤ÎÀá¤â»²¾È¤¹¤ë¤³¤È)¡£

EINTR

WNOHANG ¤¬ÀßÄꤵ¤ì¤Æ¤ª¤é¤º¡¢¶Ø»ß (block) ¤µ¤ì¤Æ¤¤¤Ê¤¤¥·¥°¥Ê¥ë¤ä SIGCHLD ¤ò¼õ¿®¤·¤¿¡£

EINVAL

options °ú¤­¿ô¤¬ÉÔÀµ¤Ç¤¢¤ë¡£

½àµò

SVr4, 4.3BSD, POSIX.1-2001.

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$ ./a.out &

Child PID is 32360

[1] 32359

$ kill -STOP 32360

stopped by signal 19

$ kill -CONT 32360

continued

$ kill -TERM 32360

killed by signal 15

[1]+  Done                    ./a.out

$



#include <sys/wait.h>

#include <stdlib.h>

#include <unistd.h>

#include <stdio.h>



int

main(int argc, char *argv[])

{

    pid_t cpid, w;

    int status;



    cpid = fork();

    if (cpid == -1) { perror("fork"); exit(EXIT_FAILURE); }



    if (cpid == 0) {            /* Code executed by child */

        printf("Child PID is %ld\n", (long) getpid());

        if (argc == 1)

            pause();                    /* Wait for signals */

        _exit(atoi(argv[1]));



    } else {                    /* Code executed by parent */

        do {

            w = waitpid(cpid, &status, WUNTRACED | WCONTINUED);

            if (w == -1) { perror("waitpid"); exit(EXIT_FAILURE); }



            if (WIFEXITED(status)) {

                printf("exited, status=%d\n", WEXITSTATUS(status));

            } else if (WIFSIGNALED(status)) {

                printf("killed by signal %d\n", WTERMSIG(status));

            } else if (WIFSTOPPED(status)) {

                printf("stopped by signal %d\n", WSTOPSIG(status));

            } else if (WIFCONTINUED(status)) {

                printf("continued\n");

            }

        } while (!WIFEXITED(status) && !WIFSIGNALED(status));

        exit(EXIT_SUCCESS);

    }

}

´ØÏ¢¹àÌÜ

_exit(2), clone(2), fork(2), kill(2), ptrace(2), sigaction(2), signal(2), wait4(2), pthread_create(3), signal(7)