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多進(jin)(jin)程(cheng)編程(cheng)中(zhong)會可能(neng)會產生僵尸進(jin)(jin)程(cheng)，這(zhe)些僵尸進(jin)(jin)程(cheng)不斷蠶食系統資源，是系統變得越來(lai)越慢直(zhi)至死亡，這(zhe)種(zhong)情況在(zai)并(bing)發模型中(zhong)體(ti)現的(de)尤為突出。這(zhe)里分(fen)析下我們在(zai)多進(jin)(jin)程(cheng)編程(cheng)中(zhong)如(ru)何解決這(zhe)樣的(de)問題。

首(shou)先我(wo)們(men)寫一個(ge)例(li)子：

#include

#include

#include

int main(int argc, char **argv)

{

int pid;

pid = fork();

if (pid > 0) {

 printf("this is parent process, pid = %d\n", getpid());

while(1);

} else if (pid == 0) {

 printf("this is child process, pid = %d\n", getpid());

printf("child process exit\n");

} else {

printf("create child process failed\n");

}

return 0;

}

本例中: 父進程創建(jian)子進程，進程完成(cheng)移動工作后退出。運行效果如下：

this is parent process, pid = 3538

this is child process, pid = 3539

child process exit

使用ps -aux查看進程狀(zhuang)態

按照幫助文檔中說明：R為運行態，Z為僵尸(zombie)態。

回收僵尸進(jin)程我們(men)可(ke)以用如下方(fang)法：

使(shi)用wait()或waitpid()函數。

#include

#include

pid_t wait(int *status);

pid_t waitpid(pid_t pid, int *status, int options);

wait: 父進程調用(yong)等待(dai)任(ren)一子進程退出。等同于(yu)waitpid(-1, &status, 0);

waitpid：

使用waitpid回收僵尸(shi)進(jin)程，如下：

C++ Code

#include

#include

#include

#include

#include

int main(int argc, char **argv)

{

int pid, cpid;

pid = fork();

if (pid > 0) {

printf("this is parent process, pid = %d\n", getpid());

while(1) {

cpid = waitpid(-1, NULL, 0);

fprintf(stdout, "waitpid pid = %d: %s\n", cpid, strerror(errno));

sleep(1);

}

} else if (pid == 0) {

printf("this is child process, pid = %d\n";, getpid());

printf("child process exit\n");

} else {

printf("create child process failed\n");

}

return 0;

}

運行結果：

this is parent process, pid = 4085

this is child process, pid = 4086

child process exit

waitpid pid = 4086: Success

waitpid pid = -1: No child processes

waitpid pid = -1: No child processes
  ps -aux查看發(fa)現原(yuan)來(lai)程序運行(xing)過程僵尸態的(de)子進(jin)程已經不(bu)在了。已經不(bu)在了。