fread() 사용법좀 문의 드립니다

char buffer[50];
 
FILE *fp;
 
fp = fopen("/dev/ttyS0", "r");
 
int fd = fileno(fp);
 
struct termios options;
tcgetattr(tvfd, &options);
cfsetispeed(&options, B38400);
cfsetospeed(&options, B38400);
options.c_cflag |= (CLOCAL | CREAD);
options.c_cflag &= ~PARENB;
options.c_cflag &= ~CSTOPB;
options.c_cflag &= ~CSIZE;
options.c_cflag |= CS8;
 
tcsetattr(tvfd, TCSANOW, &options);
 
fread(buffer, 50, 1, fp);
 
fclose(fp);