User Input being skipped - c

Question

still making my way through C Programming Absolute Beginner's Guide.
I am at the example about Structures and I cannot figure out what is going wrong. When I compile and run the code, the first two questions run fine, but after it prompts for "How much did the book cost?", when I enter the input for this one, the next two questions get posted together. I have no idea why. I think I have the code written as shown in the book. I have read online that gets is not code but I am not sure why at this point. Any guidance would once again be greatly appreciated!
//This header file defines a structure for information about a book
struct bookInfo {
char title[40];
char author[25];
float price;
int pages;
};
/*This program gets the bookInfo structure by including structurePractice.h
and asks the user to fill in three structures and then prints them*/
//First, include the header file
#include "structurePractice.h"
#include <stdio.h>
int main()
{
int ctr;
struct bookInfo books[3]; //Array of 3 structure variables
//Get information about each book from the user
for (ctr = 0; ctr < 3; ctr++)
{
printf("What is the name of the book #%d?\n", (ctr+1));
gets(books[ctr].title);
puts("Who's is the author? ");
gets(books[ctr].author);
puts("How much did the book cost? ");
scanf(" $%f", &books[ctr].price);
puts("How many pages are in the book? ");
scanf(" %d", &books[ctr].pages);
getchar(); //Clears last newline for next loop
}
//Print a header line and then loop through and print the info
printf("\n\nHere is the collection of books: \n");
for (ctr = 0; ctr < 3; ctr++)
{
printf("#%d: %s by %s", (ctr+1), books[ctr].title, books[ctr].author);
printf("\nIt is %d pages and costs $%.2f", books[ctr].pages, books[ctr].price);
printf("\n\n");
}
return (0);
}

Answer 1

You have a typo in your scanf.
scanf(" $%f", &books[ctr].price);
^
|
here
That says you want a $ followed by a decimal number. If the user does not input a dollar sign, scanf will read nothing. The input will remain on the input buffer. It will be read by the next scanf.
This is one of the many problems with scanf. Because scanf mixes up reading input with parsing input, if the input does not match the expected format it will remain in the input buffer. Instead, read and parse separately with fgets (not gets) and sscanf. It's also important to check that the input was read else books[ctr].price will contain garbage.
// Declare a buffer once outside the loop. Reuse it for each fgets call.
// BUFSIZ is a constant for the natural I/O buffer size of your platform.
char buf[BUFSIZ];
puts("How much did the book cost? ");
// Read only as much as the buffer can handle. This is what makes fgets safe,
// and gets unsafe.
fgets(buf, sizeof(buf), stdin);
// sscanf returns the number of items matched. Check if they all matched.
if( sscanf(buf, " %f", &books[ctr].price) != 1) {
printf("Sorry, '%s' doesn't look like a price.", buf);
// Set it to something or else it will be garbage.
books[ctr].price = 0;
}
A real program would loop until it gets valid input. The important thing is to read the buffer, then parse it, and check if the parsing worked. Later on you might write a little function to package up this prompting code.