如何通过执行exec来终止正在运行另一个程序的子进程

Question

我正在我的主程序中执行fork,并在子进程中执行exec,这将运行另一个程序.现在我想终止子进程(即exec调用的程序)并返回主程序(或父程序).我怎么能实现这一点..我尝试用ctrl + c,但它杀死父进程和孩子也.请帮助我.

/*This is main.c*/

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <signal.h>
#include <sys/wait.h>

void sig_int(void);
void sig_term(void);

pid_t pid,ppid;

int main(char argc,char **argv){

int n;
char ch;

printf("***********Application to start or stop services**********\n");

do
{
    printf("Enter 1 to start service no.1\n");
    printf("Enter 2 to start service no.2\n");
    printf("Enter 3 to start service no.3\n");

    scanf("%d",&n);
    if(fork() == 0)
    {
        switch(n)
        {
            case 1: printf("starting service no. 1..\n");
                printf("checking whether the given service is     already running...\n");
            //  system("./det.sh ./test")   
                pid = getpid();
                printf("child process pid = %d\n",pid);
//                  signal(SIGINT,(void *)sig_int);
//                  signal(SIGTERM,(void *)sig_term);
                  //execl("/var/vR_main","vR_main",argv[1],argv[2],argv[3],argv[4],NULL);
                execl("./test","test",0,0);//will run test.c
                break;

            case 2: printf("starting service no. 2..\n");
                break;

            case 3: printf("starting service no. 3..\n");
                break; 

        }

    }
    else
    {   
        int status;
        wait(&status);  
            if (WIFEXITED(status))
                printf("CHILD exited with %d\n", WEXITSTATUS(status));

            if (WIFSIGNALED(status))
                printf("signaled by %d\n", WTERMSIG(status));

            if (WIFSTOPPED(status))      
                printf("stopped by %d\n", WSTOPSIG(status));
//          sleep(2);
        ppid = getpid();
        printf("%d\n",ppid);
//          wait();
        printf("\nDo you want to continue...y/n:");
        scanf(" %c",&ch);
    }
}while(ch == 'y');

return 0;   

}

void sig_int(void)
{
printf("caught signal\n");
kill(pid,SIGKILL);
//  signal(SIGINT,SIG_DFL);
//  exit(0);
}

void sig_term(void)
{
printf("killing the process\n");
signal(SIGINT,SIG_DFL);
//  exit(0);
}

/*This is test.c*/

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <signal.h>

void sig_int(void);
void sig_term(void);

pid_t pid;
int main()
{
//  int a=10,b=40,c=50,max;

    pid = getpid();
printf("exec pid = %d\n",pid);

while (1)
{

    signal(SIGINT,(void *)sig_int);
    signal(SIGTERM,(void *)sig_term);
}
//  max=a>b?a>c?a:c:b>c?b:c;
//  printf("%d\n",max);
}
void sig_int(void)
{
printf("caught signal\n");
//  signal(SIGINT,SIG_DFL);
kill(pid,SIGKILL);
//  exit(0);

}

void sig_term(void)
{
printf("killing the process\n");
signal(SIGINT,SIG_DFL);
//  exit(0);
}

现在我要杀死"测试应用程序"(由exec调用),并返回父进程或"else块"继续该程序.

Answer 1

您需要执行以下操作:

1. 做a kill(pid, SIGTERM)首先 - 这为子进程提供了一个优雅终止的机会
2. 等一段时间(使用sleep).这段时间取决于子进程优雅关闭所需的时间.
3. 使用waitpid(pid, &status, WNOHANG)检查返回值.如果该过程没有中止,请执行步骤4
4. 做a kill(pid, SIGKILL)然后通过做收获僵尸waitpid(pid, &status, 0).

这些步骤可确保您为子进程提供关闭信号处理程序,并确保您没有僵尸进程.

Answer 2

POSIX为此定义了kill(2)系统调用：

kill(pid, SIGKILL);