assignment from incompatible pointer type [-Wincompatible-pointer-types]

Question

I'm new to c programming. I'm learning pointers in c, i tested simple file operation. In order to overcome overwrite the values in txt file. I declare file globally and inside the method i initialize the local pointer address to global pointer address. my intention is use the same memory location. By using the same memory location carry out the file operations . Please be kind enough to find my program below.

FILE *f;// global pointer.

void myTest(char* val) {
    //d is local pointer.
    FILE *d = fopen("file.txt", "w");
        f=&d;
    if (f == NULL)
    {
     printf("Error opening file!\n");
         exit(1);
    }
   // print the data
   fprintf(f, "%s\n",val);

}

int main(void) {

    myTest("test");
    fclose(f);
}

warning: assignment from incompatible pointer type [-Wincompatible-pointer-types] f=&d; After i run the bin file i get the Segmentation fault (core dumped) Error.

Answer 1

d is a FILE * , so &d is a FILE ** . That can't be assigned to f which is a FILE * .

What you want is f=d . Or just get rid of d entirely:

f = fopen("file.txt", "w");