如何从文件中获取信息，将其放入数组并获取数组的大小？

Question

而不是为for循环放入40我想获得数组的长度，这是我想要存储文件中的信息的地方。我会使用strlen或sizeof吗？总的来说，我将如何从文件中获取信息，然后将其存储在数组中，以获得40循环所在的for循环中的数组大小。谢谢。另外我假设使用strlen，对吗？

Int40 *loadPlainText(char *fname){//declare function
        int i; //for eventual for loop
        char c;//declare character c
        Int40 *Point=createInt40(); //call the create function because it returns a pointer to the int40 struct that holds an array filled with 0s
        //something has to catch the value that the function returns. thats why its equal to  structure
        FILE* ifp = fopen(inputFilename, "r");//opens thew file in read mode
        int arr[40];//declare an array
        for(i=0;i<=40;i++){//for loop
            fscanf(ifp, "%c", &arr[i]);//read file into an array
            Point->digits[i]=c;
        }//end for loop
        return Point;//return the pointer
    }//end function