Trying to read double from user, getting segmentation fault

Question

I'm writing a function to get input from the user where it only accepts a double value, if a wrong value is entered the user gets another chance to enter a double. I'm getting a segmentation fault whenever I input any numbers.

double ReadDouble(){
   double *ret;
   char buff[100];
   printf("Please enter a double ");
   while(fgets(buff, sizeof(buff), stdin) != 0){
      if(sscanf(buff, "%lf", ret) == 1){
         return *ret;
      }
      else{
         printf("Invalid input, please enter a double ");
      }
   }
   return EOF;
}

Answer 1

#include<stdlib.h>
#include<stdio.h>
double ReadDouble(){
   // you will return a double so you can directly declare it as a double and gives its address to the sscanf
   // if you declare it as double* you should allocate memory for it otherwise its not pointing to anything
   double ret;
   char buff[100];
   printf("Please enter a double ");

   while(fgets(buff, sizeof(buff), stdin) != 0){
     // passing the address of ret like this &ret to sscanf
      if(sscanf(buff, "%lf", &ret) == 1){
         return ret;
      }
      else{
         printf("Invalid input, please enter a double ");
      }
   }
   return EOF;
}

int main(){
printf("%lf ",ReadDouble());
}