【操作系统】编制实现进程的管道通信的程序

#include<stdio.h>
#include<stdlib.h>
#include<signal.h>
#include<unistd.h>
#define NUM 2 
int pid[NUM+1],fd[2],i,ri;
char S[40];//string
void mysend(){//child send message
    sprintf(S,"Child process %d is sending a message!\n",i);
    write(fd[1], S, 40);//write pipe
    kill(pid[0],17);//send signal to father
    exit(0);
}
void myreceive(){//father receive message
    read(fd[0], S, 40);//read pipe
    printf("%s",S);//show message
    if(i<NUM)kill(pid[++i],17);//send signal to next child
    else{while(wait(NULL)!=-1);exit(0);}//no next child so end
}
void fatherfun(){//father process
    i=1;
    signal(17,myreceive);//sign
    kill(pid[i],17);//send signal
    while(1);//wait
}
void childfun(){//child process
    signal(17,mysend);//sign
    while(1);//wait
}
int main(){
    pipe(fd);//build pipe
    pid[0]=getpid();//save father pid
    for(i=2;i<=NUM;i++)if(pid[i]=fork()){if(i==NUM)fatherfun();}else{childfun();break;}//make child
    return 0;
}