#include<stdio.h>
#include<unistd.h>
int main()
{
        pid_t pid;
        int pfd[2];  //定义两个文件描述符，放在数组中
        int ret=pipe(pfd); //定义管道
        if(ret==-1)
        {
                perror("pipe error:");
                exit(1);
        }
        pid=fork();
        if(pid==-1)
        {
                perror("fork error:");
                exit(1);
        } else if(pid==0)
        {
                close(pfd[1]);   //关闭子进程写端口
                char buf[1024]={0};
                int ret=read(pfd[0],buf,sizeof(buf)); //从管道读数据
                write(STDOUT_FILENO,buf,ret);  
        }else
        {
                close(pfd[0]);  //关闭父进程读端口
                write(pfd[1],"hello world\n",sizeof("hello world")); //向管道写数据
        }
        return 0;
}

//写端程序
#include<stdio.h>
#include<unistd.h>
#include<sys/stat.h>
#include<sys/types.h>
#include<fcntl.h>
#include<string.h>
int main()
{
        //当前目录有一个myfifo文件
        //打开fifo文件
        int fd=open("myfifo",O_WRONLY);
        //写
        char buf[256]={0};
        int num=1;
        while(1)
        {
                memset(buf,0x00,sizeof(buf));
                sprintf(buf,"newdata%d",num++);
                write(fd,buf,sizeof(buf));
                sleep(1);
                //循环写
        }
        //关闭描述符
        close(fd);
        return 0;
}

//读端程序
#include<stdio.h>
#include<sys/types.h>
#include<sys/stat.h>
#include<string.h>
#include<unistd.h>
#include<fcntl.h>
int main()
{
        int fd=open("myfifo",O_RDONLY);
        char buf[256]={0};
        int ret;
        while(1)
        {
                ret=read(fd,buf,sizeof(buf));
                if(ret>0)
                {
                        printf("%s\n",buf);
                }
        }
        close(fd);
        return 0;

}

#include<stdio.h>
#include<unistd.h>
#include<sys/types.h>
#include<sys/stat.h>
#include<fcntl.h>
#include<sys/mman.h>
#include<string.h>
int main()
{
        int fd=open("mem.txt",O_RDWR);

        //创建映射
        char *mem=mmap(NULL,8,PROT_READ|PROT_WRITE,MAP_SHARED,fd,0);
        //PRIVATE 不修改文件
        //char *mem=mmap(NULL,8,PROT_READ|PROT_WRITE,MAP_PRIVATE,fd,0);
        if(mem==MAP_FAILED)
        {
                perror("mmap error");
                return 0;
        } 
        //拷贝数据
        strcpy(mem,"i am you");
        //释放mmap
        munmap(mem,8);
        close(fd);
        return 0;
}

#include<stdio.h>
#include<unistd.h>
#include<sys/types.h>
#include<sys/stat.h>
#include<fcntl.h>
#include<sys/mman.h>
#include<sys/wait.h>
int main()
{
        //创建映射区
        int fd=open("mem.txt",O_RDWR);
        int *mem=mmap(NULL,4,PROT_READ|PROT_WRITE,MAP_SHARED,fd,0);
        if(mem==MAP_FAILED)
        {
                perror("mmap error:");
                return 0;
        }
        //fork子进程
        pid_t pid=fork();
        //父进程和子进程交替修改数据
        if(pid==0)
        {
                //子进程
                *mem=100;
                printf("child,*mem=%d\n",*mem);
                        sleep(3);
                printf("child,*mem=%d\n",*mem);

        }
        else if(pid>0)
        {
                //父进程
                sleep(1);
                printf("parent,*mem=%d\n",*mem);
                *mem=1001;
                printf("parent,*mem=%d\n",*mem);
                wait(NULL);
        }
        munmap(mem,4);
        close(fd);
        return 0;
}

int *mem=mmap(NULL,4,PROT_READ|PROT_WRITE,MAP_SHARED|MAP_ANON,-1,0);

//读端
#include<stdio.h>
#include<unistd.h>
#include<sys/types.h>
#include<sys/stat.h>
#include<fcntl.h>
#include<sys/mman.h>

typedef struct Student{
        int sid;
        char sname[20];
}Student;
int main(int argc,char *argv[])
{
　　　　 if(argc!=2)
{
　　　　 printf("./a.out filename");
　　　　 return 0;
}

        //open file
        int fd=open(argv[1],O_RDWR);
        //mmap
        int length=sizeof(Student);
        Student * stu=mmap(NULL,length,PROT_READ|PROT_WRITE,MAP_SHARED,fd,0);
        if(stu==MAP_FAILED)
{
        printf("map err:");
        return 0;
}
//read data
        while(1)
{
        printf("sid = %d, sname = %s \n",stu->sid,stu->sname);
        sleep(1);
}
        munmap(stu,length);
        close(fd);
        return 0;
}

//写端
#include<stdio.h>
#include<unistd.h>
#include<sys/types.h>
#include<sys/stat.h>
#include<fcntl.h>
#include<sys/mman.h>

typedef struct Student{
        int sid;
        char sname[20];
}Student;
int main(int argc,char* argv[])
{
        if(argc!=2)
        {
                printf("./a.out filename\n");
                return 0;
        }
        //1.open file
        int fd=open(argv[1],O_RDWR|O_CREAT|O_TRUNC,0666);
        int length=sizeof(Student);
        int num=1;
        ftruncate(fd,sizeof(length));
        //2.mmap
        Student * stu=mmap(NULL,length,PROT_READ|PROT_WRITE,MAP_SHARED,fd,0);
        if(stu==MAP_FAILED)
        {
                printf("mmap err:");
                return 0;
        }
        //3.修改内存数据
        while(1)
        {
                stu->sid=num;
                sprintf(stu->sname,"xiaoming-%03d",num++);
                sleep(1);
        }
        //4.释放映射区 关闭文件
        munmap(stu,length);
        close(fd);
        return 0;
}