C while循環無限循環EOF不起作用

Question

我在while循環中遇到EOF問題。 當輸入EOF時，它似乎並不會簡單地結束，而是……

我該如何解決它並使while循環停止並繼續前進。 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。 這很簡單。 在while循環中， while(scanf("%d", &integer) != EOF)不必像這樣設置，而是這樣理解(scanf("%d", &integer)) EOF。 要在DOS中簡單地調用它，請在最后一個輸入上使用“ Ctrl + Z”。 即“ number ^ Z”是使用“ Ctrl + Z”后的外觀。對於遇到此問題的任何人，這也是此問題的更好且有效的代碼。

#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

scanf返回成功轉換的元素數。 如果不能進行任何轉換，則返回EOF僅針對文件結尾返回（在Unix上為Control-D）。

因此，您應該修改程序以保存scanf的返回值，然后分別測試其0和EOF 。

將integer變量與EOF進行比較也是沒有意義的，因為您可能只知道EOF是負整數。 閱讀scanf手冊頁，了解它的作用以及何時何地返回什么。 那將解決難題。 :-)

好了，還有更多提示。 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 2

您沒有將整數值與EOF進行比較。 您正在將scanf結果與EOF進行比較。在這里，每次輸入1值時，scanf結果將為1。

因此，evrrytime while循環條件失敗並生成無限循環。 另外，如果您是EOF，那么您將輸入什么字符以結束循環？ 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）;

....

... printf（“輸入1繼續”）;

的scanf（ “％d”，＆檢查）;

} while（check == 1）;

Answer 3

針對EOF，0和1測試scanf()的結果。

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");
}
...

Answer 4

更新：我發現我做錯了。 這很簡單。 在while循環中，while（scanf（“％d”，＆integer）！= EOF）不必像這樣設置，而是這樣理解（scanf（“％d”，＆integer））EOF。 要在DOS中簡單地調用它，請在最后一個輸入上使用“ Ctrl + Z”。 即“ number ^ Z”是使用“ Ctrl + Z”后的外觀。對於遇到此問題的任何人，這也是此問題的更好且有效的代碼。

#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;
}