Check if input is float else stop

Question

scanf(\"%f\", &num);

I have to check if thats a valid float variable and stop executing if it has symbols like @ or !

Answer 1

You cannot check for both of your conditions in scanf. I would suggest reading whole input into a string, look for special characters. Once this test passes, try re-processing it into a string via sscanf. To search for special characters there is a strpbrk defined in string.h

char* specials = "%@!";
char* buffer[SOME_SIZE];
double value;
int err;

scanf("%s", buffer);
if( strpbrk(buffer, specials) ) return SPECIAL_FOUND;
err = sscanf(buffer, "%f", &value);
if(err <= 0) return NOT_VALID_INPUT; //NOTE: there should probably be not EOF case

// process your value

Note: I did not check the code it's a rough idea to play with.