创建僵尸进程 [英] Create zombie process
问题描述
我对创建僵尸进程感兴趣.据我了解,僵尸进程发生在父进程在子进程之前退出时.但是,我尝试使用以下代码重新创建僵尸进程:
I am interested in creating a zombie process. To my understanding, zombie process happens when the parent process exits before the children process. However, I tried to recreate the zombie process using the following code:
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
int main ()
{
pid_t child_pid;
child_pid = fork ();
if (child_pid > 0) {
exit(0);
}
else {
sleep(100);
exit (0);
}
return 0;
}
但是,此代码将在执行后立即退出,这是预期的.但是,像我一样
However, this code exits right after execute which is expected. However, as I do
ps aux | grep a.out
我发现a.out只是作为正常进程运行,而不是我期望的僵尸进程.
I found a.out is just running as a normal process, rather than a zombie process as I expected.
我正在使用的操作系统是ubuntu 14.04 64位
The OS I am using is ubuntu 14.04 64 bit
推荐答案
报价:
据我所知,僵尸进程发生在父进程在子进程之前退出的时候.
To my understanding, zombie process happens when the parent process exits before the children process.
这是错误的.根据 man 2 wait
(请参见注释):>
This is wrong. According to man 2 wait
(see NOTES) :
终止但尚未等待的孩子变成了僵尸".
A child that terminates, but has not been waited for becomes a "zombie".
因此,如果要创建一个僵尸进程,在fork(2)
之后,子进程应为exit()
,父进程应为sleep()
,然后再退出,这使您有时间观察ps(1)
.
So, if you want to create a zombie process, after the fork(2)
, the child-process should exit()
, and the parent-process should sleep()
before exiting, giving you time to observe the output of ps(1)
.
例如,您可以使用下面的代码代替您的代码,并在sleep()
ing时使用ps(1)
:
For instance, you can use the code below instead of yours, and use ps(1)
while sleep()
ing:
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
int main(void)
{
pid_t pid;
int status;
if ((pid = fork()) < 0) {
perror("fork");
exit(1);
}
/* Child */
if (pid == 0)
exit(0);
/* Parent
* Gives you time to observe the zombie using ps(1) ... */
sleep(100);
/* ... and after that, parent wait(2)s its child's
* exit status, and prints a relevant message. */
pid = wait(&status);
if (WIFEXITED(status))
fprintf(stderr, "\n\t[%d]\tProcess %d exited with status %d.\n",
(int) getpid(), pid, WEXITSTATUS(status));
return 0;
}
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