C while循環無限循環EOF不起作用

Question

我在while循環中遇到了EOF問題。它似乎並沒有簡單地結束時EOF進入，而是這樣做...

我該如何解決它，並有while循環停下來繼續前進。謝謝。

#define _CRT_SECURE_NO_WARNINGS 
    #include <stdio.h> 
    #include <limits.h> 

    void findLargestandSmallest(int integer, int* largest, int* smallest, int* average, int count); 

    int main(void) 
    { 
     //Local Declaration 
     int integer; 
     int largest; 
     int smallest; 
     int average; 
     int count; // number count 

     //Starting statemnets 
     smallest = INT_MAX; 
     largest = INT_MIN; 
     count = 0; 

     // Starting prompts 
     printf("\nHello this program will take in intagers and print"); 
     printf("\nout the largest, smallest and avarage of integers"); 
     printf("\nenterd int."); 
     printf("\nPlease enter in a integer "); 

     while (scanf("%d", &integer) != EOF) 
     { 
      if (integer != EOF) 
      { 
       count++; 
       findLargestandSmallest(integer, &largest, &smallest, &average, count); 
      } 
      else 
      { 
       printf("\n \n"); 
      } 
     } 

     printf("\nThe largest number entered is %d and the smallest", largest); 
     printf("\nwas %d and the average of all the numbers is %d\n", smallest, average); 
     return 0; 
    } 

    void findLargestandSmallest(int integer, int *largest, int *smallest, int *average, int count) 
    { 
     int x; // just a holder variable 

     // finds average 
     x = 0; 
     x += integer; 
     *average = (x/count); 

     // Finds smallest and largest 
     if (integer <= *smallest) 
     { 
      *smallest = integer; 
     } 
     if (integer >= *largest) 
     { 
      *largest = integer; 
     } 
     printf("Enter another integer or <EOF> to quit "); 
     return; 
    } 


    [1]: http://i.stack.imgur.com/P0307.png 

更新：我發現我做錯了什麼。這很簡單。在while循環while(scanf("%d", &integer) != EOF)不要像那樣設置它，但是像這樣可以理解EOF的(scanf("%d", &integer))。要在DOS中簡單地調用它，請在上次輸入中使用「Ctrl + Z」。即「數字^ Z」是它使用「Ctrl + Z」後的樣子。對於遇到這個問題的其他人來說，這個問題也是更好的工作代碼。

#define _CRT_SECURE_NO_WARNINGS 
#include <stdio.h> 
#include <limits.h> 

void findLargestandSmallest(int integer, int* largest, int* smallest); 

int main(void) 
{ 
    //Local Declaration 
    int integer; 
    int largest; 
    int smallest; 
    int average; 
    int sum; 
    int count; 

    //Starting statemnets 
    smallest = INT_MAX; 
    largest = INT_MIN; 
    count = 0; 
    sum = 0; 

    // Starting prompts 
    printf("\n--------------------------------------------------------"); 
    printf("\n- Hello, this program will take in intagers and print -"); 
    printf("\n- out the largest, smallest, and avarage of the  -"); 
    printf("\n- integers enterd.         -"); 
    printf("\n- NOTE: To quit: use \"Ctrl+Z\" on the last integer  -"); 
    printf("\n- you enter i.e \"number^z\"      -"); 
    printf("\n--------------------------------------------------------\n"); 
    printf("\nEnter integers\n"); 

    // Finds largest and smallest number 
    while (scanf("%d", &integer)) 
    { 
     sum += integer; 
     count++; 
     findLargestandSmallest(integer, &largest, &smallest); 
    } 

    // Finds average 
    count--; 
    average = (sum/count); 

    // End prompts 
    printf("\n--------------------------------------------------------"); 
    printf("\nThe largest number entered was %d, the smallest", largest); 
    printf("\nwas %d, and the average of all the numbers is %d.", smallest, average); 
    printf("\n--------------------------------------------------------"); 
    printf("\nGoodbye\n"); 
    return 0; 
} 

void findLargestandSmallest(int integer, int *largest, int *smallest) 
{ 
    if (integer < *smallest) 
    { 
     *smallest = integer; 
    } 
    if (integer > *largest) 
    { 
     *largest = integer; 
    } 
    return; 
} 

Answer 1

更新：我發現我在做什麼錯。這很簡單。在while循環while（scanf（「％d」，& integer）！= EOF）不要這樣設置，但是像這樣（scanf（「％d」，& integer））EOF被理解。要在DOS中簡單地調用它，請在上次輸入中使用「Ctrl + Z」。即「數字^ Z」是它使用「Ctrl + Z」後的樣子。對於遇到這個問題的其他人來說，這個問題也是更好的工作代碼。

#define _CRT_SECURE_NO_WARNINGS 
#include <stdio.h> 
#include <limits.h> 

void findLargestandSmallest(int integer, int* largest, int* smallest); 

int main(void) 
{ 
    //Local Declaration 
    int integer; 
    int largest; 
    int smallest; 
    int average; 
    int sum; 
    int count; 

    //Starting statemnets 
    smallest = INT_MAX; 
    largest = INT_MIN; 
    count = 0; 
    sum = 0; 

    // Starting prompts 
    printf("\n--------------------------------------------------------"); 
    printf("\n- Hello, this program will take in intagers and print -"); 
    printf("\n- out the largest, smallest, and avarage of the  -"); 
    printf("\n- integers enterd.         -"); 
    printf("\n- NOTE: To quit: use \"Ctrl+Z\" on the last integer  -"); 
    printf("\n- you enter i.e \"number^z\"      -"); 
    printf("\n--------------------------------------------------------\n"); 
    printf("\nEnter integers\n"); 

    // Finds largest and smallest number 
    while (scanf("%d", &integer)) 
    { 
     sum += integer; 
     count++; 
     findLargestandSmallest(integer, &largest, &smallest); 
    } 

    // Finds average 
    count--; 
    average = (sum/count); 

    // End prompts 
    printf("\n--------------------------------------------------------"); 
    printf("\nThe largest number entered was %d, the smallest", largest); 
    printf("\nwas %d, and the average of all the numbers is %d.", smallest, average); 
    printf("\n--------------------------------------------------------"); 
    printf("\nGoodbye\n"); 
    return 0; 
} 

void findLargestandSmallest(int integer, int *largest, int *smallest) 
{ 
    if (integer < *smallest) 
    { 
     *smallest = integer; 
    } 
    if (integer > *largest) 
    { 
     *largest = integer; 
    } 
    return; 
} 

Answer 2

scanf返回成功轉換的元素數量。如果無法轉換，則返回0. EOF僅返回文件結尾（在Un​​ix上是Control-D）。

所以你應該修改程序來保存scanf的返回值，然後分別測試0和EOF。

這也是沒有意義的integer變量與EOF比較，因爲所有你所能知道的EOF是，它是一個負整數。閱讀scanf手冊頁，瞭解它的作用以及它在何時何地返回的內容。這將解決這個難題。 :-)

好的，還有一些提示。你能理解這個嗎？

for (;;) { 
    int successfully_converted = scanf("%d", &integer); 

    if (successfully_converted == EOF) { 
     /* Do something when the user is tired of typing. */ 
     puts("Thank you for an enjoyable game.\n"); 
     exit(0); 
    } else if (successfully_converted == 0) { 
     puts("This didn't look like an integer\n"); 
     exit(1); 
    } else { 
     /* Do something with integer. */ 
    } 
} 

Answer 3

您沒有將整數值與EOF 進行比較。您正在比較scanf結果和EOF。 這裏，當您每次輸入1個值時，scanf結果將爲1.

因此evrrytime while循環條件失敗並生成無限循環。 另外，如果你是EOF，那麼你會輸入什麼字符來結束循環？ 因此不應使用EOF。

所以我建議你使用do while循環

做

{

的scanf（ 「％d」，&整數）;

....

... 的printf（ 「請輸入1，繼續」）;

scanf（「％d」，&檢查）;

} while（check == 1）;

Answer 4

測試scanf()對EOF，0的結果，1

int cnt; 
while ((cnt = scanf("%d", &integer)) == 1) { 
    count++; 
    findLargestandSmallest(integer, &largest, &smallest, &average, count); 
} 
if (cnt == 0) { 
    printf("Something other than an integer was entered.\n"); 
} 
else if (cnt == EOF) { 
    printf("EOF or I/O Error occurred.\n"); 
} 
// Add the following for debug if desired 
else { 
    printf("Should _never get here!\n"); 
} 
...