How to read from a specific file using a pointer to that file?

Question

I am trying to read from .txt file using a pointer diff to file,
FILE* diff = NULL;
diff = fopen("file.txt", "r");

But it shows me that fopen maybe unsafe, I changed it to fopen_s (as recommended) and now I have 3 more errors :

' a value of type "errno_t" cannot be assigned to an entity of type "FILE*" '
' argument of type "const char*" is incompatible with parameter of type "FILE*" '
' too few arguments in function call'

How to fix this?

Answer 1

here is the snippet of code :

FILE *fp;

fopen_s(&fp, "testFile.txt", "r+");

fclose(fp);

Answer 2

Thanks! Now it works perfectly!