我应该如何修改 C 中的 fork() 以使其运行良好？

发布于 2024-07-17 08:23:09 字数 944 浏览 3 评论 0原文

我不明白为什么我的代码不起作用。

这是我的代码。我不知道为什么会出现错误段。有人可以向我解释一下原因吗？

#include <iostream>
#include <string>
#include <sys/types.h>
#include <unistd.h>

int id_process;

void manager_signal () {
    kill (id_process, SIGKILL);
    kill (getppid(),SIGKILL);
}

int main () {
    id_process = fork ();
    if (id_process==-1) {
        perror("ERROR to create the fork");
    } else {
        if ( id_process != 0 ) {
            printf("Father´s ID is %d \n", getpid());   
            alarm(5);
            (void) signal (SIGALRM, manager_signal);
            sleep (20);
            printf ("Running to where the father can be\n");
            alarm (0);          
        } else {
            printf ("CHildren´s ID is %d \n", getpid ());
            for (;;) {
                printf ( "Children RUN FOREVER ^^");
                sleep (2);
            }
        }
    }
    return 0;
}

原文

I dont understand why my code does not work.

This is my code. I don't know why I'm get an error segment. Could somebody explain the reason to me?

#include <iostream>
#include <string>
#include <sys/types.h>
#include <unistd.h>

int id_process;

void manager_signal () {
    kill (id_process, SIGKILL);
    kill (getppid(),SIGKILL);
}

int main () {
    id_process = fork ();
    if (id_process==-1) {
        perror("ERROR to create the fork");
    } else {
        if ( id_process != 0 ) {
            printf("Father´s ID is %d \n", getpid());   
            alarm(5);
            (void) signal (SIGALRM, manager_signal);
            sleep (20);
            printf ("Running to where the father can be\n");
            alarm (0);          
        } else {
            printf ("CHildren´s ID is %d \n", getpid ());
            for (;;) {
                printf ( "Children RUN FOREVER ^^");
                sleep (2);
            }
        }
    }
    return 0;
}

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南渊 2024-07-24 08:23:10

您的问题有点难以理解，因为您没有真正解释错误是什么，但我确实有一个问题，我确信这是相关的。

为什么“父亲”进程会杀死其子进程及其父进程？难道它不应该杀死它的孩子和它自己（id_process和getpid()而不是getppid()这是父PID)吗？

这似乎就是问题所在。当我在 Cygwin 下运行它时，它会杀死我的 shell（真烦人）。如果我将其更改为 kill (getpid(),SIGKILL);，它会在五秒后正常终止，并显示以下输出：

$ vi qq.cpp ; g++ -o qq qq.cpp ; ./qq.exe
Fathers ID is 6016
Childrens ID is 4512
Children RUN FOREVER ^^
Children RUN FOREVER ^^
Children RUN FOREVER ^^
Children RUN FOREVER ^^
Children RUN FOREVER ^^
Killed

这是程序修改后的情况，如下所示：

#include <iostream>
#include <string>
#include <sys/types.h>
#include <unistd.h>

int id_process;

void manager_signal (int x) {
    kill (id_process, SIGKILL);
    kill (getpid(),SIGKILL);
}

int main () {
    id_process = fork ();
    if (id_process==-1) {
        perror("ERROR to create the fork");
    } else {
        if ( id_process != 0 ) {
            printf("Fathers ID is %d\n", getpid());
            alarm(5);
            (void) signal (SIGALRM, manager_signal);
            sleep (20);
            printf ("Running to where the father can be\n");
            alarm (0);
        } else {
            printf ("Childrens ID is %d\n", getpid ());
            for (;;) {
                printf ( "Children RUN FOREVER ^^\n");
                sleep (1);
            }
        }
    }
    return 0;
}

Your question is a little difficult to understand since you don't really explain what the error is, but I do have one question which I'm sure will be pertinent.

Why is the "father" process killing its child and its parent? Shouldn't it kill its child and itself (id_process and getpid() rather than getppid() which is the parent PID)?

That appears to be the problem. When I run that under Cygwin, it kills off my shell (darned annoying). If I change it to kill (getpid(),SIGKILL);, it terminates okay after five seconds with the following output:

$ vi qq.cpp ; g++ -o qq qq.cpp ; ./qq.exe
Fathers ID is 6016
Childrens ID is 4512
Children RUN FOREVER ^^
Children RUN FOREVER ^^
Children RUN FOREVER ^^
Children RUN FOREVER ^^
Children RUN FOREVER ^^
Killed

This is with the program modified as follows:

#include <iostream>
#include <string>
#include <sys/types.h>
#include <unistd.h>

int id_process;

void manager_signal (int x) {
    kill (id_process, SIGKILL);
    kill (getpid(),SIGKILL);
}

int main () {
    id_process = fork ();
    if (id_process==-1) {
        perror("ERROR to create the fork");
    } else {
        if ( id_process != 0 ) {
            printf("Fathers ID is %d\n", getpid());
            alarm(5);
            (void) signal (SIGALRM, manager_signal);
            sleep (20);
            printf ("Running to where the father can be\n");
            alarm (0);
        } else {
            printf ("Childrens ID is %d\n", getpid ());
            for (;;) {
                printf ( "Children RUN FOREVER ^^\n");
                sleep (1);
            }
        }
    }
    return 0;
}

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