注：未知原因，创建出一个危险的文件

#include<sys/types.h>
#include<sys/stat.h>
#include<iostream>
#include<unistd.h>
#include<fcntl.h>

using namespace std;

int main(){
	char* buf = new char[8];	//can't alloc 1024?
	int fd = open("./fileIO.txt", O_CREAT|O_RDWR|O_APPEND);
	
	//chmod("fileIO.txt",644);
	//const char* filename
	//flag O_CREAT|O_RDONLY|O_WRONLY|O_RDWR|O_APPEND


	if(fd<0){
		cout<<"open file failed!"<<endl;
	}

	int m = write(fd,"test\n",50);
	//int file_id
	//char* buf
	//int lenth
	//return real lenth

	cout<<m<<endl;
	
	close(fd);

	fd = open("./fileIO.txt",O_RDONLY);
	int n = read(fd,buf,500);
	//char* buf (empty buf)	

	cout<<n<<endl;
	printf("%s\n",buf);
	close(fd);
	return 0;
}