如何在C中修復字符串或指針？

Question

我正在從事轉換編程任務。 我們必須將lbs轉換為kgs，反之亦然，但是當我運行我的代碼時，這是輸出

100kgs = 220（空白）

在空白處，字母“ lbs”不會出現。 知道為什么嗎？

#include <stdio.h> 
#include <string.h>


void convert_weight(int weight1, char units1[], int* weight2, char units2[])
{

    int l = strcmp(units1, "lbs");
    int k = strcmp(units1, "kgs");


    if(l == 0) {

        *weight2 = weight1 /2.2;
        units2 = "kgs";
    }
    else {
        if(k == 0)
        {

        *weight2 = weight1 *2.2;
        units2 ="lbs";
    }
    }


}

int main() {
  char newline, another = 'y';
  int weight1, weight2;
  char units1[4], units2[4]; // length 4 because of '\0'
  while (another == 'y') {
    printf("Enter a weight and the units of the weight (lbs or kgs)\n");
    scanf("%d %s", &weight1, units1);
    convert_weight(weight1, units1, &weight2, units2);
    printf("%d %s = %d %s\nAnother (y or n)\n", weight1, units1, weight2, units2); 
    scanf("%c%c", &newline, &another)    ;
  }
  return 0;
}

Answer 1

您需要將單位字符串復制到unit2而不僅僅是在convert_weight分配它。

我不記得該函數，但我認為是：

strncpy(unit2,"xxx",max);

其中max是您還必須通過的新邊界檢查int ，在調用代碼中作為sizeof(unit2)進行，因此：

convert_weight(..., units2,sizeof(unit2));

Answer 2

用作轉換：

void convert_weight(int weight1, char units1[4], int *weight2, char units2[4])
{
  if (strcmp(units1, "lbs") == 0)
    {
      *weight2 = weight1 / 2.2;
      strcpy(units2, "kgs");
    }
  else if (strcmp(units1, "kgs") == 0)
    {
      *weight2 = weight1 * 2.2;
      strcpy(units2, "lbs");
    }
  else
    printf("Invalid units: %s\n", units1);
  units2[3] = 0; // '\0'                                                                                                                                                                                    
}