if not exist, failed

Hello
I try a function "if not exist" but this will give my Warnings, please what would meant this warnings?

Code:

---

#include<stdio.h>
int main() {
  FILE *fname;
  if (fname = fopen("a.txt", "r")) {
      fclose(fname);
      printf("file exists");
  } else {
      printf("file doesn't exist");
  }
}

---

to compile using "geany" and "GCC" for Windows.

Warning from Compiler

Code:

---

gcc -Wall -c "ifex.c" (im Verzeichnis: C:\Temp\tcc)
ifex.c: In function 'main':
ifex.c:4:8: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
    5 |    if (fname = fopen("a.txt", "r")) {
      |        ^~~~~
Kompilierung erfolgreich beendet.

---

please, if there problems with the GCC Compiler ? i see also
that in the meantime the Compiler Option i need to change from GCC 2 g++, and then the file will blow up over 2-3mb, for 10 lines Code?

That warning is legit. The compiler thinks you meant to use '==' instead of '='.
Two options:

Code:

---

...
if ((fname = fopen("a.txt", "r"))) {
...

---

or

Code:

---

#include <stdio.h>

int main(void) {
  FILE *fname = NULL;

  fname = fopen("a.txt", "r");

  if (fname != NULL) {
      fclose(fname);
      printf("file exists");
  } else {
      printf("file doesn't exist");
  }
  return 0;
}

---

Thanks Rstanley
I made your changes and are running very well thanks meny time.

Strange thing are also, i uninstall Geany my Compiler Environment, and install after that codeblocks, here are running both version my&our without any Warnings.

I would thanks also for your fast answer!
Regards

Or see this example.

Code:

---

/** opnclose.c */
#include <stdio.h>        /*  printf, fopen, fclose  */
#include <stdlib.h>      /*  exit                  */

#define READ "r"

int main(int argc, char *argv[])
 {
  FILE *fz;

  if (argc != 2)                             
  {
    printf("\n\nSyntax: opnclose datei[.ext]");
    exit(0);
  }

  if ((fz = fopen(argv[1], READ)) == NULL)   
  printf("\n\nFailure:could not open file %s\n", argv[1]);
  else
  {
    fclose(fz);                             
    printf("\n\nFile %s closed.", argv[1]);
  }
 return 0;
}

---