Understanding Unix/Linux Programming-用户程序：play_again3

  1 /* play_again3.c
  2  * purpuse: ask if user wants another play 
  3  * better : instant response without echo
  4               set tty into no-delay mode
  5               read char , return result
  6               reset terminal mode on Internet
  7  * returns: 0 -> yes , 1 -> no 
  8  */
  9  
 10  #include <stdio.h>
 11  #include <stdlib.h>
 12  #include <fcntl.h>
 13  #include <termios.h>
 14  #include <string.h>
 15  
 16  #define ASK "Do you want another play?"
 17  #define TRIES 3
 18  #define SLEEPTIME 2
 19  #define BEEP putchar(‘\a‘);
 20 
 21 
 22  int get_response(char *);
 23  int get_ok_char(void);
 24  void set_nodelay_mode(void);
 25  void set_cr_noecho_mode(void);
 26  void tty_mode(int); 
 27  
 28  int main()
 29  {
 30      int response ;
 31      tty_mode(0);   // save tty mode
 32      set_cr_noecho_mode();
 33      set_nodelay_mode();
 34      response = get_response(ASK);
 35      tty_mode(1);   // restore tty mode
 36      return response ;
 37  }
 38  
 39  int get_response(char * qiz)
 40  {
 41      int input ;
 42      int maxtries = TRIES ;
 43      printf("%s(y/n)" , qiz);
 44      fflush(stdout);
 45      while(1)
 46      {
 47         BEEP ;
 48         sleep(SLEEPTIME);
 49         input = tolower(get_ok_char()) ;
 50         if(input == ‘y‘)
 51         {
 52             printf("\n");
 53             return 0 ;
 54         }
 55         if(input == ‘n‘)
 56         {
 57             printf("\n");
 58             return 1 ;
 59         }
 60         if(maxtries -- <= 0 )
 61         {
 62             printf("\n");
 63             return 2 ;
 64         }
 65         BEEP ;
 66      }
 67  }
 68  
 69 int get_ok_char(void)
 70 {
 71     int c ;
 72     while( (c = getchar() ) != EOF && strchr("yYnN" , c ) == NULL )
 73         ;
 74     return c ;
 75 }
 76 
 77 void set_cr_noecho_mode(void)
 78 {
 79     struct  termios ttystate ;
 80     tcgetattr(0 , &ttystate);
 81     ttystate.c_lflag &= ~ICANON ;   // No Buffering
 82     ttystate.c_lflag &= ~ECHO ;
 83     ttystate.c_cc[VMIN] = 1 ;   //Get one char one time 
 84     tcsetattr( 0 , TCSANOW , &ttystate);    
 85 }
 86 
 87 void set_nodelay_mode(void)
 88 {
 89     int termflags ;
 90     termflags = fcntl(0 , F_GETFL);
 91     termflags |= O_NDELAY ;
 92     fcntl(0 , F_SETFL , termflags) ;
 93 }
 94 
 95 void tty_mode(int mode)
 96 {
 97     static struct termios original_mode ;// 设置静态结构体变量
 98     if(mode == 0 )
 99     {
100         tcgetattr( 0 , & original_mode);// 存储原有设置
101     }
102     else
103     {
104         //还原原有设置
105         if( tcsetattr(0 , TCSANOW , & original_mode) == -1 )
106         {
107             perror("Restore tty settings failed!\n");
108         }
109     }
110 }