How can one allocate an array dynamically in C and populate it with the contents of a file being read?

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To allocate an array dynamically in C, you can use the malloc() function which allocates a block of memory of specified size in bytes and returns a pointer to the first byte of the allocated memory. Here's an example of dynamically allocating an array of integers:

int* arr;
int size = 10; // or any other desired size
arr = (int*) malloc(size * sizeof(int));

To populate the array with the contents of a file being read, you can open the file using fopen() function, read the contents using fgets() or fscanf() function, and store them in the dynamically allocated array. Here's an example of reading integers from a file and storing them in a dynamically allocated array:

int* arr;
int size = 10; // or any other desired size
arr = (int*) malloc(size * sizeof(int));

FILE* fp = fopen("file.txt", "r");
if (fp == NULL) {
    printf("Error: File not found!\n");
    exit(1);
}

int i = 0;
int num;
while (fscanf(fp, "%d", &num) == 1) {
    if (i >= size) { // if array is full, resize it
        size *= 2;
        arr = (int*) realloc(arr, size * sizeof(int));
    }
    arr[i] = num; // store the read number in the array
    i++;
}

fclose(fp);

In this example, we first allocate an array of size 10 using malloc(). We then open the file file.txt and read integers using fscanf(). We keep storing the read numbers in the array until the end of file is reached. If the array becomes full, we resize it using realloc() function to double its size. Finally, we close the file using fclose() function.