read.c

来自「一个驱动程序开发 一个系统调用 内附文档 非常详细」· C语言 代码 · 共 56 行

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

#define BUFSIZE 1024*100
#define MAXDATALEN (sizeof(int))


struct timespec ts;
int end = 0;
void clean_exit(int dummy) {
	end = 1;
}

main() {
	int fd, len, wlen;
	char receive[BUFSIZE];
	char writestr[32*BUFSIZE];
	int tmp = sizeof(char);
	char tmp2;
	int k, i, o;
	
	signal(SIGTERM, clean_exit);	
	signal(SIGINT, clean_exit);	

	fd = open("/dev/mpcdevice0", O_RDWR);

	if( fd == -1) {
		printf("open error...\n");
		exit(0);
	}
	wlen = 0;k=1;
	while(1){
		len = read(fd, receive, 1);
		if (len<=0){
			close(fd);
			return 0;
		}
		wlen += sprintf (writestr+wlen, "%c", receive[0]);
		if (receive[0]=='\n') break;
	}
	len=write(STDOUT_FILENO,writestr, wlen);
	if (len>0) printf("read OK...\n");
	
	close(fd);
}