所有数组元素在C中都是相同的fget？ [英] all array elements are the same fgets in C?

问题描述

因此，当前我的程序使用这样的硬编码数组：

So currently my program uses a hard-coded array like this:

char *array[] = {"array","ofran","domle","tters", "squar"}

基本上n个字符串 n length（一个n * n网格）。然后，我将这些值视为2D数组。因此，我将访问array [y] [x]并使用相应的ASCII进行比较操作和数学运算。

Basically n strings of n length "an n*n grid. I then treat the values like a 2D array. So I will access array[y][x] and do comparison operations and math using the corresponding ASCII.

我想允许在程序中实现各种大小（n * n）（最多32个）的文本文件，而不是对其进行硬编码，但是我在使用fgets时遇到了问题。

I wanted to allow text files of various sizes (n*n) (up to 32) be implemented in my program instead of hard coding it. But am having issues with using fgets.

我当前用于获取和存储文件信息的函数如下：

My current function for getting and storing the file information looks like this:

char *array[32];
char buffer[32];
FILE *fp = fopen("textfile.txt","r");

int n = 0;
while(fgets(buffer, 32, fp)){
    array[i] = buffer;
    n++;
}
fclose(fp);

，但是 array的所有值都相同（它们是最后一个字符串）。以上。如果我将array [0]打印到array [4]，我将从代码中得到

but all values of "array" are the same (they are the last string). So with the example values above. If I printed array[0] to array [4] I get

值

squar
squar
squar
squar
squar

期望值：

array
ofran
domle
tters
squar

推荐答案

array [i] = buffer 只是将相同的指针分配给 array 的所有元素。您需要在此处动态分配内存：

array[i] = buffer just assigns the very same pointer to all elements of array. You need dynamic memory allocation here:

char *array[32];
char buffer[32];
FILE *fp = fopen("textfile.txt","r");

int n = 0;
while(fgets(buffer, 32, fp)){
    array[i] = strdup(buffer);  // allocate memory for a new string
                                // containing a copy of the string in buffer
    n++;
}
fclose(fp);

为简洁起见，此处未进行错误检查。另外，如果输入文件包含多于32行，您也会遇到麻烦。

No error checking is done here for brevity. Also if the input file contains more than 32 lines you'll run into trouble.

如果 strdup 不存在在您的平台上：

if strdup does not exist on your platform:

char *strdup(const char *str)
{
  char *newstring = malloc(strlen(str) + 1);  // + 1 for the NUL terminator
  if ( newstring )
    strcpy(newstring, str);
  return(newstring);
}

为简便起见，这里也没有进行错误检查。

Again no error checking is done here for brevity.

这篇关于所有数组元素在C中都是相同的fget？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！