//#define _POSIX_MAPPED_FILES 1#include <sys/mman.h>#include <stdio.h>#include <sys/types.h>#include <sys/stat.h>#include <fcntl.h>#include <unistd.h>int main(){	int nLength;	int fd,mapped_mem;	unsigned char *pz;	int ret;	ret=getpagesize();	printf("page size=%d\n",ret);	fd=open("1.txt",O_RDWR);	//fd=open("1.txt",O_RDONLY);	printf("fd=%d\n",fd);	if(fd<=0){		printf("open file 1.txt error\n");		return 0;	}	nLength=lseek(fd,0,SEEK_END);	printf("file size %d sizes\n",nLength);	lseek(fd,0,SEEK_SET);	mapped_mem=(char *)mmap(0,nLength,PROT_WRITE | PROT_READ,MAP_SHARED,fd,0);	pz=mapped_mem;	printf("mapped=%x\n",mapped_mem);	//printf("pz=%s\n",pz);	return 0;}