文件进程

 子进程读取父进程数据

#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>

void ReadFile(int fd)
{	
	char buf[32] = {0};

	lseek(fd, 0, SEEK_SET);

	int ret = read(fd, buf, sizeof(buf));
	if (-1 == ret)
	{
		perror("read");
		exit(1);
	}
	printf("Child read from txt : %s\n", buf);
}

void WriteFile(int fd)
{
	char buf[32] = "helloworld";

	int ret = write(fd, buf, strlen(buf));
	if (-1 == ret)
	{
		perror("write");
		exit(1);
	}
}

int main()
{
	pid_t pid;
	int fd;

	fd = open("file.tmp", O_RDWR | O_CREAT | O_EXCL, S_IRWXU);
	if (-1 == fd)
	{
		perror("open");
		exit(1);
	}

	pid = fork();
	if (-1 == pid)
	{
		perror("fork");
		exit(1);
	}
	else if (0 == pid)   //子进程读数据   子进程可以继承父进程已经打开的文件描述符
	{
		sleep(1);
		ReadFile(fd);
	}
	else                 //父进程写数据
	{
		WriteFile(fd);
		sleep(2);
	}

	return 0;
}