fgets和處理CTRL + D輸入

Question

我抓住用戶的一些標準輸入，如果用戶按下CTRL + D ，我想顯示一個錯誤並終止程序。我想也許我的問題可能與陷入一段時間循環有關;

int readInput(){ 
    char buff[10]; 
    int count = 0; 
    int counter; 
    printf("Enter random number: "); 
    fgets(buff, 10, stdin); 
    if ((int) strtol(buff, NULL, 10) == 0){ 
     printf("Error reading number. \n"); 
     return 0; //This will get hit if the user presses CTRL+D at this input. 
    } 
    counter = atol(buff); 
    while (count < counter){ 
     printf("Enter a label: "); 
     fgets(buff, 10, stdin); 
     if ((int) strtol(buff, NULL, 10) == 0){ 
     printf("Error reading label"); 
     return 0; //This will not get hit if the user presses CTRL+D at this input, but why? 
     //I've also tried assigning a variable to 0, breaking out of the loop using break; and returning the variable at the end of the function but that also does not work. 

     //the rest of the while loop continues even if user hit CTRL+D 
     printf("Enter Value: "); 
     fgets(buff, 10, stdin); 
     //..rest of while loop just gets other inputs like above 
     count++; 
    } 

//termination happens in main, if readInput returns a 0 we call RETURN EXIT_FAILURE; 

我不明白，爲什麼在第一次輸入，如果用戶按下CTRL + d，程序作出相應的響應，但第二次它完全忽略它。

Answer 1

在Linux上，Ctrl + D生成EOF，所以你需要每次檢查返回值fgets()。當遇到EOF，fgets()返回一個空指針

if (fgets(buff, 10, stdin) == NULL) 
    print_error();