//p6.7.c#include <unistd.h>#include <fcntl.h>#include <sys/types.h>#include <sys/stat.h>#include <unistd.h>#include <stdlib.h>#include <stdio.h>#include <linux/soundcard.h>#define Audio_Device "/dev/dsp"/*  不同的聲音文件有著不同的播放參數，這些參數可以使用file命令獲得*/#define Sample_Size 16  #define Sample_Rate 8000 /* 取樣率 */int play_sound(char *filename){  struct stat stat_buf;  unsigned char *buf = NULL;  int handler,fd;  int result;  int arg,status;/*打開聲音文件，將文件讀入內存*/  fd = open(filename, O_RDONLY);  if (fd<0)      return -1;  if (fstat(fd, &stat_buf)) {     close(fd);     return -1; }  if (!stat_buf.st_size) {	close(fd);	return -1;  }  buf = malloc(stat_buf.st_size);  if (!buf) {	close(fd);	return -1;  }  if (read(fd, buf, stat_buf.st_size) < 0) {	free(buf);	close(fd);	return -1;  } /*打開聲卡設備，并設置聲卡播放參數，這些參數必須與聲音文件參數一致 */  handler = open(Audio_Device, O_WRONLY);  if (handler == -1) {	perror("open Audio_Device fail");	return -1; }   arg=Sample_Rate;  status=ioctl(handler,SOUND_PCM_WRITE_RATE,&arg);  if(status==-1){        perror("error from SOUND_PCM_WRITE_RATE ioctl");        return -1;}  arg=Sample_Size;  status=ioctl(handler,SOUND_PCM_WRITE_BITS,&arg);  if(status==-1){	  perror("error from SOUND_PCM_WRITE_BITS ioctl");	  return -1;  }  result=write(handler,buf,stat_buf.st_size);  if(result==-1){       perror("Fail to play the sound!");       return -1;  }  free(buf);  close(fd);  close(handler);  return result;}void main(void){  play_sound("/root/Online.wav");}