Dynamic String Input - using scanf(“%as”)

Question

I am trying to read input using scanf and storing into char * dynamically as specified by GCC manual , But it is giving a compile time error.

  char *string;
  if (scanf ("%as",&string) != 1){
    //some code
  }
  else{
   printf("%s\n", *string);
   free(string);
   //some code
  }

Answer 1

The a modifier to scanf won't work if you are compiling with the -std=c99 flag; make sure you aren't using that.

If you have at least version 2.7 of glibc, you can and should use the m modifier in place of a .

Also, it is your responsibility to free the buffer.

Answer 2

Do you have GNU extensions enabled? Standard C doesn't have a modifier at all.

Answer 3

I've had limited experience with GCC, but I've never seen a %a modifier for scanf . Have you tried replacing the %a with %s in the third line you provided?

Answer 4

'Dynamic String Input' with scanf("%as") will work if the -ansi or -std=c89 flag is enabled.
Compile using gcc -ansi

Or else you can use scanf("%ms")