管道呼叫和同步

#include <stdio.h>
#include <stdlib.h>

#define SIZE 30
#define Error_(x) { perror(x); exit(1); }
int main(int argc,char *argv[]) {

    char message[SIZE];
    int pid,status,ret,fd[2];

    ret = pipe(fd);
    if(ret == -1) Error_("Pipe creation");

    if((pid = fork()) == -1) Error_("Fork error");

    if(pid == 0){ //child process: reader (child wants to receive data from the parent)
        close(fd[1]); //reader closes unused ch.
        while( read(fd[0],message,SIZE) > 0 )
                printf("Message: %s",message);
        close(fd[0]);
    }
    else{//parent: writer (reads from STDIN,sends data to the child)
        close(fd[0]);
        puts("Tipe some text ('quit to exit')");
        do{
            fgets(message,SIZE,stdin);
            write(fd[1],SIZE);
        }while(strcmp(message,"quitn") != 0);
        close(fd[1]);
        wait(&status);
    }
}

代码工作正常但我无法解释原因！父进程和子进程之间没有明确的同步.如果子进程在parent之前执行,则read必须返回0并且进程结束,但由于某种原因它等待父执行.你怎么解释这个？也许我错过了什么.

(编辑)的