Linux Certif

Toute la documentation sur la certification Linux LPI

system

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system - ¥·¥§¥ë¥³¥Þ¥ó¥É¤Î¼Â¹Ô

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#include <stdlib.h>



int system(const char *command);

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system() ¤Ï command ¤Ç»ØÄꤷ¤¿¥³¥Þ¥ó¥É¤ò /bin/sh -c command ¤Î·Á¤Ç¼Â¹Ô¤¹¤ë¡£»ØÄꤷ¤¿¥³¥Þ¥ó¥É¤¬½ªÎ»¤¹¤ì¤Ð¤³¤Î´Ø¿ô¤â½ªÎ»¤¹¤ë¡£ ¥³¥Þ¥ó¥É¼Â¹ÔÃæ¤Ï¡¢ SIGCHLD ¤Ï¥Ö¥í¥Ã¥¯¤µ¤ì¡¢ SIGINT ¤È SIGQUIT ¤Ï̵»ë¤µ¤ì¤ë¡£

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¥¨¥é¡¼¤¬È¯À¸¤·¤¿¾ì¹ç (fork(2) ¤Ë¼ºÇÔ¤·¤¿¾ì¹ç¤Ê¤É)¡¢-1 ¤òÊÖ¤¹¡£ ¤½¤¦¤Ç¤Ê¤±¤ì¤Ð¡¢¥³¥Þ¥ó¥É¤Î¥¹¥Æ¡¼¥¿¥¹¤òÊÖ¤¹¡£ ¸å¼Ô¤Î¾ì¹ç¡¢¥¹¥Æ¡¼¥¿¥¹¤Ï wait(2) ¤ÇÄêµÁ¤µ¤ì¤Æ¤¤¤ë¥Õ¥©¡¼¥Þ¥Ã¥È¤ÇÊ֤äƤ¯¤ë¡£ ½¾¤Ã¤Æ¡¢¥³¥Þ¥ó¥É¤Î½ªÎ»¥³¡¼¥É¤Ï WEXITSTATUS(status) ¤ÇÆÀ¤ë¤³¤È¤¬½ÐÍè¤ë¡£ /bin/sh ¤¬¼Â¹Ô½ÐÍè¤Ê¤«¤Ã¤¿¾ì¹ç¡¢ ½ªÎ»¥¹¥Æ¡¼¥¿¥¹¤Ï¥³¥Þ¥ó¥É¤¬ exit(127) ¤ò¼Â¹Ô¤·¤¿¾ì¹ç¤ÈƱ¤¸¤Ë¤Ê¤ë¡£

command ¤ÎÃͤ¬ NULL ¤Î¤È¤­¤Ï¡¢ system() ¤Ï¥·¥§¥ë¤¬ÍøÍѲÄǽ¤Ê¤é¥¼¥í°Ê³°¤ÎÃͤòÊÖ¤·¡¢ÍøÍÑÉԲĤʤ饼¥í¤òÊÖ¤¹¡£

system() ¤Ï¾¤Î»Ò¥×¥í¥»¥¹¤Î¥¦¥¨¥¤¥È¥¹¥Æ¡¼¥¿¥¹¤Ë¤Ï±Æ¶Á¤òÍ¿¤¨¤Ê¤¤¡£

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C89, C99, POSIX.1-2001.

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µ¡Ç½¸¡ºº¥Þ¥¯¥í¤Ç¤¢¤ë _XOPEN_SOURCE ¤¬ÄêµÁ¤µ¤ì¤¿¾ì¹ç¤Ë¤Ï¡¢ wait(2) ¤ÇÀâÌÀ¤µ¤ì¤Æ¤¤¤ë¥Þ¥¯¥í·² (WEXITSTATUS() Åù) ¤¬ <stdlib.h> ¤ò¥¤¥ó¥¯¥ë¡¼¥É¤¹¤ë¤ÈÍøÍѲÄǽ¤Ë¤Ê¤ë¡£

´û¤Ë½Ò¤Ù¤¿¤è¤¦¤Ë¡¢ system() ¤Ï SIGINT ¤È SIGQUIT ¤ò̵»ë¤¹¤ë¡£ ¤è¤Ã¤Æ¥ë¡¼¥×¤«¤é system() ¤ò¸Æ¤Ö¥×¥í¥°¥é¥à¤Ï¡¢ °Ê²¼¤ÎÎã¤Î¤è¤¦¤Ë»Ò¥×¥í¥»¥¹¤Î½ªÎ»¾õÂÖ¤ò¼«Ê¬¤Ç¥Á¥§¥Ã¥¯¤·¤Æ¤ª¤«¤Ê¤¤¤È¡¢ ÃæÃǤǤ­¤Ê¤¯¤Ê¤ë¤«¤â¤·¤ì¤Ê¤¤¡£

    while(something) {

        int ret = system("foo");



        if (WIFSIGNALED(ret) &&

            (WTERMSIG(ret) == SIGINT || WTERMSIG(ret) == SIGQUIT))

                break;

    }

set-user-ID ¤ä set-group-ID ¤ÎÆø¢¤ò¤â¤Ä¥×¥í¥°¥é¥à¤ÎÃæ¤Ç¤Ï system() ¤ò»È¤Ã¤Æ¤Ï¤¤¤±¤Ê¤¤¡£¤Ê¤¼¤Ê¤é¡¢¤¢¤ë´Ä¶­ÊÑ¿ô¤Î̤ÃΤÎÃͤˤè¤Ã¤Æ ¥·¥¹¥Æ¥à¤Î°ÂÁ´¤¬Â»¤Ê¤ï¤ì¤ë¤«¤é¤Ç¤¢¤ë¡£Âå¤ï¤ê¤Ë exec(3) ´ØÏ¢¤Î´Ø¿ô·²¤ÎÃæ¤Ç execlp(3) ¤È execvp(3) °Ê³°¤Î´Ø¿ô¤ò»ÈÍѤ¹¤Ù¤­¤Ç¤¢¤ë¡£ ¼ÂºÝ¤Î¤È¤³¤í¡¢ system() ¤Ï /bin/sh ¤¬ bash ¥Ð¡¼¥¸¥ç¥ó 2 ¤Ç¤¢¤ë¥·¥¹¥Æ¥à¤Ç¤Ï¡¢ set-user-ID ¤ä set-group-ID ¤ÎÆø¢¤ò»ý¤Ä¥×¥í¥°¥é¥à¤«¤é¤ÏÀµ¤·¤¯Æ°ºî¤·¤Ê¤¤¡£ ¤Ê¤¼¤Ê¤é¡¢bash ¥Ð¡¼¥¸¥ç¥ó 2 ¤Ï¥¹¥¿¡¼¥È¥¢¥Ã¥×»þ¤ËÆø¢¤òÍî¤È¤¹¤«¤é¤Ç¤¢¤ë¡£ (Debian ¤Ç¤Ï¡¢sh ¤È¤·¤Æµ¯Æ°¤µ¤ì¤¿»þ¤Ë¤Ï¤³¤Î¤è¤¦¤ÊÆ°ºî¤ò¹Ô¤Ê¤ï¤Ê¤¤¤è¤¦¤Ë ½¤Àµ¤µ¤ì¤¿ bash ¤òÍѤ¤¤Æ¤¤¤ë)

glibc 2.1.3 ¤è¤êÁ°¤Î¥Ð¡¼¥¸¥ç¥ó¤Ç¤Ï¡¢ command ¤¬ NULL ¤Î¾ì¹ç¤Ë /bin/sh ¤¬ÍøÍѲÄǽ¤«¤É¤¦¤«¤Î¥Á¥§¥Ã¥¯¤Ï¼ÂºÝ¤Ë¤Ï¹Ô¤ï¤º¡¢ ¤¤¤Ä¤Ç¤âÍøÍѲÄǽ¤Ç¤¢¤ë¤È¤ß¤Ê¤·¤Æ¤¤¤¿¡£ system() ¤Ï¤³¤Î¾ì¹ç¤Ë¾ï¤Ë 1 ¤òÊÖ¤·¤Æ¤¤¤¿¡£ POSIX.1-2001 ¤Ç¤Ï¥·¥§¥ë¤¬Ä󶡤µ¤ì¤Æ¤¤¤ë¤È¤¤¤¦É¸½à¤Ë½àµò¤·¤¿¼ÂÁõ¤ò Í׵ᤷ¤Æ¤¤¤ë¤¬¡¢glibc 2.1.3 °Ê¹ß¤Ç¤Ï¥·¥§¥ë¤Î¥Á¥§¥Ã¥¯¤ò¼Â¹Ô¤·¤Æ¤¤¤ë¡£ ¤Ê¤¼¤Ê¤é¡¢¸Æ¤Ó½Ð¤·¸µ¤Î¥×¥í¥°¥é¥à¤¬ system() ¤ò¸Æ¤Ó½Ð¤¹¤è¤êÁ°¤Ë (POSIX.1-2001 ¤Ç¤Ïµ¬Äꤵ¤ì¤Æ¤¤¤Ê¤¤) chroot(2) ¤ò¸Æ¤Ó½Ð¤·¤Æ¤¤¤¿»þ¤Ë¤Ï¡¢¥·¥§¥ë¤¬ÍøÍѲÄǽ¤Ç¤Ê¤¤¾ì¹ç¤ä¼Â¹Ô²Äǽ¥Õ¥¡¥¤¥ë ¤Ç¤Ê¤¤¾ì¹ç¤¬¤¢¤ë¤«¤é¤Ç¤¢¤ë¡£

¼Â¹Ô¤·¤¿¥·¥§¥ë¥³¥Þ¥ó¥É¤¬ 127 (/bin/sh ¤Î¸Æ¤Ó½Ð¤·¤Ë¼ºÇÔ¤·¤¿»þ¤ËÊÖ¤¹ÃÍ) ¤òÊÖ¤¹¤³¤È¤â¹Í¤¨¤é¤ì¤ë¡£ ¤½¤Î¤¿¤á¡¢¥×¥í¥°¥é¥à¤Ï (¥ê¥¿¡¼¥ó¥³¡¼¥É¤ò¸«¤ë¤À¤±¤Ç¤Ï) execve(2) ¤Î¸Æ¤Ó½Ð¤·¤¬¼ºÇÔ¤·¤¿¤³¤È¤ò³Î¼Â¤ËÃΤ뤳¤È¤Ï¤Ç¤­¤Ê¤¤¡£

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sh(1), signal(2), wait(2), exec(3)