test_read.c

内核空间地址向用户空间地址的映射实例

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

int main(int argc,char **argv)
{
	
	int fd = 0;
	char read_buffer[20] = {'\0'};
	int n =0;

	//fd = open("/dev/hello",O_RDWR | O_CREAT | O_TRUNC);
	//fd = open("/dev/hello",O_RDONLY | O_NONBLOCK);
	fd = open("/dev/hello",O_RDONLY );
	printf("fd=%d\n",fd);
	if(fd < 0) {
		perror("/dev/hello");
		return -1;
	}

	n = read(fd,read_buffer,sizeof(read_buffer)-1);
	printf("read return %d\n",n);
	if(n < 0)
		printf("errorno=%d,error type:%s\n",errno,strerror(errno));
	if(n>=0)
		printf("read_buffer=%s\n",read_buffer);


	close(fd);

	return 0;
}