Ò»ÇÐÖ»ÊÇ¿ªÊ¼

来源: BlogBus 原始链接: http://www.blogbus.com:80/blogbus/blog/diary.php?diaryid=156326 存档链接: https://web.archive.org/web/20040624204453id_/http://www.blogbus.com:80/blogbus/blog/diary.php?diaryid=156326

Ò»ÇÐÖ»ÊÇ¿ªÊ¼ Linux, ǶÈëʽϵͳ, ´®¿ÚͨÐÅ, PALM OS, Bluetooth ... Êǹ¤×÷ÖÐÕýÓõ½µÄ

Java, software engineering, ÒÔ¼°ÆäËûµÄºÜ¶à¼¼Êõ£¬ÊÇÎÒ¸ÐÐËȤµÄ <<<Linux Ï´´½¨ÁÙʱÎļþ | Ê×Ò³ | OOP vs. NOOP>>> ¹ØÓÚ fork ºÍ¸¸×Ó½ø³ÌµÄÀí½â ʱ¼ä: 04/04/28 CU ÉϹØÓÚ fork µÄһЩÌÖÂÛ£¬½²µÃ±È½ÏÇå³þ£¬°ïÖúÎÒÀí½âÁ˶à½ø³ÌµÄ¸ÅÄî ´úÂë: #include <unistd.h> #include <sys/types.h> main () { pid_t pid; pid=fork(); if (pid < 0) printf("error in fork!"); else if (pid == 0) printf("i am the child process, my process id is %d\n",getpid()); else printf("i am the parent process, my process id is %d\n",getpid()); } ½á¹ûÊÇ [root@localhost c]# ./a.out i am the child process, my process id is 4286 i am the parent process, my process id is 4285 ÎÒ¾ÍÏë²»µ½ÎªÊ²Ã´Á½Ðж¼´òÓ¡³öÀ´ÁË£¬ÔÚÎÒÏëÀ´£¬²»¹ÜpidÊǶàÉÙ£¬¶¼Ó¦¸ÃÖ»ÓÐÒ»ÐвŶÔ

naiza дµ½: ÕâÀïµÄifºÍelse²»ÊÇÒÔÇ°Àí½âµÄÑ¡Ôñ·ÖÖ§¡£forkºó²úÉúµÄ×Ó½ø³ÌºÍ¸¸½ø³Ì²¢ÐÐÔËÐÐµÄ ÕâÖÖÀí½âÊDz»ÕýÈ·µÄ¡£if ºÍ else »¹ÊÇÑ¡Ôñ·ÖÖ§¡£ Ö÷ÒªµÄÔ­ÒòÊÇ£¬ fork() º¯Êýµ÷ÓÃÒ»´Î£¬·µ»ØÁ½´Î¡£ Á½´Î·µ»ØµÄÇø±ðÊÇ£º×Ó½ø³ÌµÄ·µ»ØÖµÊÇ0£¬¸¸½ø³Ì·µ»ØֵΪÐÂ×Ó½ø³ÌµÄ½ø³ÌID¡£

µ«ÊÇÖ»ÓÐÒ»¸öpid=fork(); ѽ£¬fork()·µ»ØµÄµÚ¶þ´ÎÖµÔÚʲôʱºò¸³¸øpidÄØ pidÕâ¸ö±äÁ¿ÊÇÓÐÁ½¸öµÄ£¬ ¸¸½ø³ÌÒ»¸ö£¬ ×Ó½ø³ÌÒ»¸ö¡£

Òª¸ãÇå³þforkµÄÖ´Ðйý³Ì£¬¾Í±ØÐëÏȽ²Çå³þ²Ù×÷ϵͳÖÐµÄ ¡°½ø³Ì(process)¡± ¸ÅÄî¡£Ò»¸ö½ø³Ì£¬Ö÷Òª°üº¬Èý¸öÔªËØ£º o. Ò»¸ö¿ÉÒÔÖ´ÐеijÌÐò£» o. ºÍ¸Ã½ø³ÌÏà¹ØÁªµÄÈ«²¿Êý¾Ý£¨°üÀ¨±äÁ¿£¬ÄÚ´æ¿Õ¼ä£¬»º³åÇøµÈµÈ£©£» o. ³ÌÐòµÄÖ´ÐÐÉÏÏÂÎÄ£¨execution context£©¡£ ²»·Á¼òµ¥Àí½âΪ£¬Ò»¸ö½ø³Ì±íʾµÄ£¬¾ÍÊÇÒ»¸ö¿ÉÖ´ÐгÌÐòµÄÒ»´ÎÖ´Ðйý³ÌÖеÄÒ»¸ö״̬¡£²Ù×÷ϵͳ¶Ô½ø³ÌµÄ¹ÜÀí£¬µäÐ͵ÄÇé¿ö£¬ÊÇͨ¹ý½ø³Ì±íÍê³ÉµÄ¡£½ø³Ì±íÖеÄÿһ¸ö±íÏ¼Ç¼µÄÊǵ±Ç°²Ù×÷ϵͳÖÐÒ»¸ö½ø³ÌµÄÇé¿ö¡£¶ÔÓÚµ¥ CPUµÄÇé¿ö¶øÑÔ£¬Ã¿Ò»Ìض¨Ê±¿ÌÖ»ÓÐÒ»¸ö½ø³ÌÕ¼Óà CPU£¬µ«ÊÇϵͳÖпÉÄÜͬʱ´æÔÚ¶à¸ö»î¶¯µÄ£¨µÈ´ýÖ´Ðлò¼ÌÐøÖ´Ðеģ©½ø³Ì¡£ Ò»¸ö³ÆΪ¡°³ÌÐò¼ÆÊýÆ÷£¨program counter, pc£©¡±µÄ¼Ä´æÆ÷£¬Ö¸³öµ±Ç°Õ¼Óà CPUµÄ½ø³ÌÒªÖ´ÐеÄÏÂÒ»ÌõÖ¸ÁîµÄλÖᣠµ±·Ö¸øij¸ö½ø³ÌµÄ CPUʱ¼äÒѾ­ÓÃÍ꣬²Ù×÷ϵͳ½«¸Ã½ø³ÌÏà¹ØµÄ¼Ä´æÆ÷µÄÖµ£¬±£´æµ½¸Ã½ø³ÌÔÚ½ø³Ì±íÖжÔÓ¦µÄ±íÏîÀïÃ棻°Ñ½«Òª½ÓÌæÕâ¸ö½ø³ÌÕ¼Óà CPUµÄÄǸö½ø³ÌµÄÉÏÏÂÎÄ£¬´Ó½ø³Ì±íÖжÁ³ö£¬²¢¸üÐÂÏàÓ¦µÄ¼Ä´æÆ÷£¨Õâ¸ö¹ý³Ì³ÆΪ¡°ÉÏÏÂÎĽ»»»(process context switch)¡±£¬Êµ¼ÊµÄÉÏÏÂÎĽ»»»ÐèÒªÉæ¼°µ½¸ü¶àµÄÊý¾Ý£¬ÄǺÍforkÎ޹أ¬²»ÔÙ¶à˵£¬Ö÷ÒªÒª¼Çס³ÌÐò¼Ä´æÆ÷pcÖ¸³ö³ÌÐòµ±Ç°ÒѾ­Ö´Ðе½ÄÄÀÊǽø³ÌÉÏÏÂÎĵÄÖØÒªÄÚÈÝ£¬»»³ö CPUµÄ½ø³ÌÒª±£´æÕâ¸ö¼Ä´æÆ÷µÄÖµ£¬»»ÈëCPUµÄ½ø³Ì£¬Ò²Òª¸ù¾Ý½ø³Ì±íÖб£´æµÄ±¾½ø³ÌÖ´ÐÐÉÏÏÂÎÄÐÅÏ¢£¬¸üÐÂÕâ¸ö¼Ä´æÆ÷£©¡£ ºÃÁË£¬ÓÐÕâЩ¸ÅÄî´òµ×£¬¿ÉÒÔ˵forkÁË¡£µ±ÄãµÄ³ÌÐòÖ´Ðе½ÏÂÃæµÄÓï¾ä£º pid=fork(); ²Ù×÷ϵͳ´´½¨Ò»¸öеĽø³Ì£¨×Ó½ø³Ì£©£¬²¢ÇÒÔÚ½ø³Ì±íÖÐÏàӦΪËü½¨Á¢Ò»¸öеıíÏнø³ÌºÍÔ­Óнø³ÌµÄ¿ÉÖ´ÐгÌÐòÊÇͬһ¸ö³ÌÐò£»ÉÏÏÂÎĺÍÊý¾Ý£¬¾ø´ó²¿·Ö¾ÍÊÇÔ­½ø³Ì£¨¸¸½ø³Ì£©µÄ¿½±´£¬µ«ËüÃÇÊÇÁ½¸öÏ໥¶ÀÁ¢µÄ½ø³Ì£¡´Ëʱ³ÌÐò¼Ä´æÆ÷pc£¬ÔÚ¸¸¡¢×Ó½ø³ÌµÄÉÏÏÂÎÄÖж¼Éù³Æ£¬Õâ¸ö½ø³ÌÄ¿Ç°Ö´Ðе½forkµ÷Óü´½«·µ»Ø£¨´Ëʱ×Ó½ø³Ì²»Õ¼ÓÐCPU£¬×Ó½ø³ÌµÄpc²»ÊÇÕæÕý±£´æÔڼĴæÆ÷ÖУ¬¶øÊÇ×÷Ϊ½ø³ÌÉÏÏÂÎı£´æÔÚ½ø³Ì±íÖеĶÔÓ¦±íÏîÄÚ£©¡£ÎÊÌâÊÇÔõô·µ»Ø£¬ÔÚ¸¸×Ó½ø³ÌÖоͷֵÀÑïïð¡£ ¸¸½ø³Ì¼ÌÐøÖ´ÐУ¬²Ù×÷ϵͳ¶ÔforkµÄʵÏÖ£¬Ê¹Õâ¸öµ÷ÓÃÔÚ¸¸½ø³ÌÖзµ»Ø¸Õ¸Õ´´½¨µÄ×Ó½ø³ÌµÄpid£¨Ò»¸öÕýÕûÊý£©£¬ËùÒÔÏÂÃæµÄifÓï¾äÖÐpid<0, pid==0µÄÁ½¸ö·ÖÖ§¶¼²»»áÖ´ÐС£ËùÒÔÊä³öi am the parent process... ×Ó½ø³ÌÔÚÖ®ºóµÄij¸öʱºòµÃµ½µ÷¶È£¬ËüµÄÉÏÏÂÎı»»»È룬ռ¾Ý CPU£¬²Ù×÷ϵͳ¶ÔforkµÄʵÏÖ£¬Ê¹µÃ×Ó½ø³ÌÖÐforkµ÷Ó÷µ»Ø0¡£ËùÒÔÔÚÕâ¸ö½ø³Ì£¨×¢ÒâÕâ²»ÊǸ¸½ø³ÌÁËŶ£¬ËäÈ»ÊÇͬһ¸ö³ÌÐò£¬µ«ÊÇÕâÊÇͬһ¸ö³ÌÐòµÄÁíÍâÒ»´ÎÖ´ÐУ¬ÔÚ²Ù×÷ϵͳÖÐÕâ´ÎÖ´ÐÐÊÇÓÉÁíÍâÒ»¸ö½ø³Ì±íʾµÄ£¬´ÓÖ´ÐеĽǶÈ˵ºÍ¸¸½ø³ÌÏ໥¶ÀÁ¢£©ÖÐpid=0¡£Õâ¸ö½ø³Ì¼ÌÐøÖ´ÐеĹý³ÌÖУ¬ifÓï¾äÖÐpid<0²»Âú×㣬µ«ÊÇpid==0ÊÇtrue¡£ËùÒÔÊä³öi am the child process... ÎÒÏëÄã±È½ÏÀ§»óµÄ¾ÍÊÇ£¬ÎªÊ²Ã´¿´ÉÏÈ¥³ÌÐòÖл¥³âµÄÁ½¸ö·ÖÖ§¶¼±»Ö´ÐÐÁË¡£ÔÚÒ»¸ö³ÌÐòµÄÒ»´ÎÖ´ÐÐÖУ¬Õ⵱ȻÊDz»¿ÉÄܵģ»µ«ÊÇÄã¿´µ½µÄÁ½ÐÐÊä³öÊÇÀ´×ÔÁ½¸ö½ø³Ì£¬ÕâÁ½¸ö½ø³ÌÀ´×Ôͬһ¸ö³ÌÐòµÄÁ½´ÎÖ´ÐС£ ÎÒµÄÌ죬²»ÖªµÀ˵Ã÷°×ÁËû¡­¡­

µ½µ×Äĸö½ø³ÌÖ´ÐÐÔÚÏÈ£¬Õâ¸öºÍ²Ù×÷ϵͳµÄµ÷¶ÈËã·¨µÈµÈºÜ¶àÒòËØÏà¹Ø¡£ÎÒ¾õµÃÀí½âÉϵÄÀ§ÄÑ£¬¹Ø¼üÔÚÓÚΪʲô»áÓÐÁ½¸öÊä³ö£¬¶ø²»ÊÇË­ÏÈË­ºó¡£

forkÖ®ºó£¬²Ù×÷ϵͳ»á¸´ÖÆÒ»¸öÓ븸½ø³ÌÍêÈ«ÏàͬµÄ×Ó½ø³Ì£¬Ëä˵ÊǸ¸×Ó¹Øϵ£¬µ«ÊÇÔÚ²Ù×÷ϵͳ¿´À´£¬ËûÃǸüÏñÐֵܹØϵ£¬Õâ2¸ö½ø³Ì¹²Ïí´úÂë¿Õ¼ä£¬µ«ÊÇÊý¾Ý¿Õ¼äÊÇ»¥Ïà¶ÀÁ¢µÄ£¬×Ó½ø³ÌÊý¾Ý¿Õ¼äÖеÄÄÚÈÝÊǸ¸½ø³ÌµÄÍêÕû¿½±´£¬Ö¸ÁîÖ¸ÕëÒ²ÍêÈ«Ïàͬ£¬µ«Ö»ÓÐÒ»µã²»Í¬£¬Èç¹ûfork³É¹¦£¬×Ó½ø³ÌÖÐforkµÄ·µ»ØÖµÊÇ0£¬¸¸½ø³ÌÖÐforkµÄ·µ»ØÖµÊÇ×Ó½ø³ÌµÄ½ø³ÌºÅ£¬Èç¹ûfork²»³É¹¦£¬¸¸½ø³Ì»á·µ»Ø´íÎó¡£ ¿ÉÒÔÕâÑùÏëÏó£¬2¸ö½ø³ÌһֱͬʱÔËÐУ¬¶øÇÒ²½µ÷Ò»Ö£¬ÔÚforkÖ®ºó£¬ËûÃÇ·Ö±ð×÷²»Í¬µÄ¹¤×÷£¬Ò²¾ÍÊÇ·Ö²íÁË¡£ÕâÒ²ÊÇforkΪʲô½ÐforkµÄÔ­Òò¡£ ÖÁÓÚÄÇÒ»¸ö×îÏÈÔËÐУ¬¿ÉÄÜÓë²Ù×÷ϵͳÓйأ¬¶øÇÒÕâ¸öÎÊÌâÔÚʵ¼ÊÓ¦ÓÃÖв¢²»ÖØÒª£¬Èç¹ûÐèÒª¸¸×Ó½ø³ÌЭͬ£¬¿ÉÒÔͨ¹ýÔ­ÓïµÄ°ì·¨½â¾ö¡£ carol ·¢±íÓÚ 04/04/28 16:20 ÒýÓÃ(Trackback0) ÆÀÂÛ ·¢±íÆÀÂÛ ×îºó¸üР[תÌù]ÕæµÄÁ˽âtelnetÂ𣿠[ͼ]Introduction to Bluetooth Record - June 15th~ [WIN CE] Ô¶³Ì¿ØÖÆ£¬Ê°빦±¶ ´Ó¿ª·¢½Ç¶È¿´ smartphone palm ÉÏÎå·N²»Í¬µÄ reset [ת] ·¨Óï The 11 Truths of Debugging [תÌù]΢ÈíSmartphoneÓ¦ÓóÌÐòÉè¼ÆÈëÃÅ smartphone Ò»ÀÀ