Linux signal

#include <stdio.h>

#include <stdlib.h>

#include <signal.h>

#include <unistd.h>

#include <sys/wait.h>



void handler(int signo)

{

    switch(signo) {

    case SIGUSR1: //处理信号 SIGUSR1

        printf("Parent : catch SIGUSR1\n");

    case SIGUSR2: //处理信号 SIGUSR2

        printf("Child : catch SIGUSR2\n");

    default:      //本例不支持

        printf("Should not be here\n");

        break;

    }

}



int main(void)

{

    pid_t ppid, cpid;

    //为两个信号设置信号处理函数

    if(signal(SIGUSR1, handler) == SIG_ERR) { //设置出错

        perror("Can't set handler for SIGUSR1");

        exit(1);

    }



    if(signal(SIGUSR2, handler) == SIG_ERR) { //设置出错

        perror("Can't set handler for SIGUSR2");

        exit(1);

    }



    ppid = getpid();//得到父进程ID



    if((cpid = fork()) < 0) {

        perror("fail to fork");

        exit(1);

    } else if(cpid == 0) { //子进程

        if(kill(ppid, SIGUSR1) == -1) {

            perror("fail to send signal");

            exit(1);

        }



        while(1);//死循环，等待父进程的信号

    } else {

        sleep(1);//休眠，保证子进程先运行，并且发送SIGUSR1信号



        if(kill(ppid, SIGUSR2) == -1) {

            perror("fail to send signal");

            exit(1);

        }



        printf("kill child\n");//输出提示



        if(kill(ppid, SIGKILL) == -1) { //发送SIGKILL信号，杀死子进程

            perror("fail to send signal");

            exit(1);

        }



        if(wait(NULL) ==-1) { //回收子进程状态，避免僵尸进程

            perror("fail to wait");

            exit(1);

        }

    }



    return;

}



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