c - 检测 stdin 上的空字符串和 C 中的 tolower 函数

Question

我目前正在用 C 编写字典程序。如何检测 stdin 上的空字符串？使用 search_for 作为我的输入。

void find_track(char search_for[])
{

        int i;
        for (i = 0; i < 5; i++) {
            if (strstr(tracks[i], search_for)){
            printf("The meaning of %s: %s\n",tracks[i], meaning[i]);

                break;
            } 
        }

        if (!strstr(tracks[i], search_for)) {
                printf("%s could not found in dictionary.\n",search_for);
            }   

}

同样，我如何使用 tolower 函数降低输入？

int main()
{
    int setloop =1;
    titlemessage();
    do {

        char search_for[80];
        char varchar;
        printf("Search for: ");
        fgets(search_for, 80, stdin);
          if(search_for[strlen(search_for)-1]=='\n')
          search_for[strlen(search_for)-1]='\0';

        find_track(search_for);
        printf("Press ENTER to start new search\n");
        //printf("Press 'q' to exit the program\n\n");

            varchar = getchar();
            if (varchar == 10) {    
                continue;
            }else {
                break;
            }
    } while (setloop = 1);
    return 0;

}

任何方法将不胜感激。

Answer 1

Detect empty string on stdin and tolower function in C

 fgets(search_for, 80, stdin);
 if(search_for[strlen(search_for)-1]=='\n')
      search_for[strlen(search_for)-1]='\0';


  if(strlen(search_for)==0)
   {
   // empty string, do necessary actions here
   }

---

char ch;

tolower()如果 ch 是一个大写字母并且有一个小写字母，则将 ch 转换为它的小写字母。如果无法进行此类转换，则返回的值不变。

   for(i = 0; search_for[i]; i++){
      search_for[i] = tolower(search_for[i]); // convert your search_for to lowercase 
    }