os

#include<stdio.h>
#include<unistd.h>
#include<sys/wait.h>
int main(){
        int fd[2];
        char buf[80];
        pid_t pid;
        pipe(fd);
        if((pid = fork()) > 0){
                printf("This is in the father process, here write a string to the pipe. ");
                char s[]="Hello world,this is write by pipe. ";
                write(fd[1],s,sizeof(s));
                close(fd[0]);
                close(fd[1]);
        }else{
                printf("This is in the child process, here read a string from the pipe. ");
                read(fd[0],buf,sizeof(buf));
                printf("%s ",buf);
                close(fd[0]);
                close(fd[1]);
        }
        waitpid(pid,NULL,0);
        return 0;
}

#include<stdio.h>
#include<unistd.h>
#include<sys/wait.h>
#include<stdlib.h>
int main(){
        int i,j,fd[2];
        char buf[100];
        pipe(fd);
        if((i = fork()) == 0){
                sprintf(buf,"child1 send message to the pipe! ");
                lockf(fd[1],1,0);
                write(fd[1],buf,50);
                sleep(1);
                lockf(fd[1],0,0);
                exit(0);
        }else if((j = fork()) == 0){
                sprintf(buf,"child2 send message to the pipe! ");
                lockf(fd[1],1,0);
                write(fd[1],buf,50);
                sleep(1);
                lockf(fd[1],0,0);
                exit(0);
        }else{
                char s[100];
                wait(0);
                read(fd[0],s,50);
                printf("%s ",s);
                wait(0);
                read(fd[0],s,50);
                printf("%s ",s);
        }return 0;}