对终端进行读写和与终端对话例程

  1 /*
  2 对终端进行读写的程序
  3 */
  4
  5 #include <stdio.h>
  6 #include <unistd.h>
  7
  8 char *menu[] =
  9 {
 10     "a - add new record",
 11     "d - delete record",
 12     "q - quit",
 13     NULL,
 14 };//定义了字符串数组
 15
 16 int getchoice(char *greet, char *choices[]);//定义了函数原型
 17
 18 int main()//主函数
 19 {
 20     int choice = 0;
 21
 22     if(!isatty(fileno(stdout)))//是终端的话返回1，不指执行循环体
 23     {
 24         fprintf(stderr,"You are not a terminal!\n");
 25         exit(1);
 26     }
 27
 28     do
 29     {
 30         choice = getchoice("Please select an action", menu);//调用函数
 31         printf("You have chosen: %c\n", choice);//打印选择的字符串
 32     } while (choice != ‘q‘);
 33     exit(0);
 34 }
 35
 36 int getchoice(char *greet, char *choices[])//核心函数
 37 {
 38     int chosen = 0;
 39     int selected;
 40     char **option;
 41
 42     do
 43     {//先无条件循环一次
 44         printf("Choice: %s\n",greet);//打印欢迎语
 45
 46         option = choices;//数组赋值给option
 47         while(*option)
 48         {//option不为空
 49             printf("%s\n",*option);//循环打印option
 50             option++;
 51         }
 52
 53         //selected = getchar();//获取用户输入单独这句在ubuntu上好像不能截取处合适的字符
 54         do{selected=getchar();}
 55         while (selected == ‘\n‘);
 56
 57         option = choices;//再次给option赋值为数组
 58         while(*option)
 59         {//不为空的时候
 60             if(selected == *option[0]) //对比数组第一个字母和选择的输入
 61             {
 62                 chosen = 1;//
 63                 break;
 64             }
 65             option++;
 66         }
 67         if(!chosen) {//有匹配的话不执行
 68             printf("Incorrect choice, select again\n");
 69         }
 70     } while(!chosen);//有匹配的话不再循环
 71     return selected;
 72 }
 73 //执行效果：
 74 /*
 75 [email protected]:~/c_program/544977-blp3e/chapter05$ ./a.out
 76 Choice: Please select an action
 77 a - add new record
 78 d - delete record
 79 q - quit
 80
 81
 82
 83 a
 84 You have chosen: a
 85 Choice: Please select an action
 86 a - add new record
 87 d - delete record
 88 q - quit
 89 d
 90 You have chosen: d
 91 Choice: Please select an action
 92 a - add new record
 93 d - delete record
 94 q - quit
 95 q
 96 You have chosen: q
 97 [email protected]:~/c_program/544977-blp3e/chapter05$
 98
 99 [email protected]:~/c_program/544977-blp3e/chapter05$ ./a.out >file
100 You are not a terminal!
101
102 */

 1 #include <stdio.h>
 2 #include <unistd.h>
 3
 4 char *menu[] = {
 5     "a - add new record",
 6     "d - delete record",
 7     "q - quit",
 8     NULL,
 9 };//定义了字符数组
10
11 int getchoice(char *greet, char *choices[], FILE *in, FILE *out);//定义了函数原形
12
13 int main()//主函数
14 {
15     int choice = 0;
16     FILE * input;
17     FILE * output;
18
19     if (!isatty(fileno(stdout))) {//是终端的话返回-1执行循环体
20         fprintf(stderr,"You are not a terminal, OK.\n");
21     }
22
23     input = fopen("/dev/tty", "r");//只读模式打开终端。返回文件流
24     output = fopen("/dev/tty", "w");//指写模式打开终端，返回文件流
25     if(!input || !output) { //出错处理
26         fprintf(stderr,"Unable to open /dev/tty\n");
27         exit(1);
28     }
29
30     do {
31         choice = getchoice("Please select an action", menu, input, output);
32         printf("You have chosen: %c\n", choice);//调用函数，打印这句话
33     } while (choice != ‘q‘);
34     exit(0);
35 }
36
37 int getchoice(char *greet, char *choices[], FILE *in, FILE *out)//核心函数
38 {
39     int chosen = 0;
40     int selected;
41     char **option;
42
43     do {
44         fprintf(out,"Choice: %s\n",greet);
45         option = choices;
46         while(*option)
47         {
48             fprintf(out,"%s\n",*option);
49             option++;//打印数组内容
50         }
51
52         do
53         {
54             selected = fgetc(in);//从输入流获取输入到selected中
55         } while (selected == ‘\n‘);
56
57         option = choices;
58         while(*option)
59          {//当数组不为空的时候
60             if(selected == *option[0]) //匹配第一个字符和输入
61             {
62                 chosen = 1;
63                 break;
64             }
65             option++;
66         }
67         if(!chosen)
68         {
69             fprintf(out,"Incorrect choice, select again\n");
70         }
71     } while(!chosen);
72     return selected;//返回匹配的输入
73 }
74
75 //执行效果
76 /*
77 [email protected]:~/c_program/544977-blp3e/chapter05$ ./a.out >file1
78 You are not a terminal, OK.
79 Choice: Please select an action
80 a - add new record
81 d - delete record
82 q - quit
83 a
84 Choice: Please select an action
85 a - add new record
86 d - delete record
87 q - quit
88 q
89 [email protected]:~/c_program/544977-blp3e/chapter05$ cat file1
90 You have chosen: a
91 You have chosen: q
92
93 */

关于怎么重定向到文件中的还是没看懂。应该是跟/dev/tty的性质有关系吧，以后学到再研究。

参考文献：

Linux程序设计 Neil Matthew