Thread: C Problem - Create a Personal Library

Hello, I am new to the forum. I need help in debugging the program as it does not produce the expected output and I can't figure out where goes wrong. I haven't completed the whole program and I am working on it part by part.

Here is my code:

Code:

#include <stdio.h>#include <stdlib.h>
#include <string.h>


struct book
{
	char *title;
	char *author;
	char *subject;
};


struct library
{
	struct book collection;
	int num_books;
	struct library *next;
};


typedef struct library lib;
typedef lib *libPtr;


void addBook(FILE *fPtr,libPtr *sPtr);
void copybook(struct book *dest,struct book *source);
void deleteBook(FILE *fPtr,libPtr *sPtr);
void searchBook(FILE *fPtr,libPtr *sPtr);
void listAuthor(FILE *fPtr,libPtr *sPtr);
void listSubject(FILE *fPtr,libPtr *sPtr);


int main()
{
	libPtr startPtr = NULL;
	int choice;
	FILE *fPtr;
	fPtr = fopen("library.txt","r");
	if (fPtr == NULL)
	{
		puts("File can't be loaded.\n");
	}
	else
	{
		while (!feof(fPtr))
		{
			fscanf(fPtr,"%d",&choice);
			switch (choice)
			{
				case 1:
					addBook(fPtr,&startPtr);
					break;
			}
		}
	}
	fclose(fPtr);
	return 0;
}


void addBook(FILE *fPtr,libPtr *sPtr)
{
	libPtr newPtr;
	libPtr currentPtr;
	libPtr previousPtr;
	struct library *myLib;
	myLib = (struct library *)malloc(sizeof(struct library));
	myLib->collection.title = (char *)malloc(sizeof(50));
	myLib->collection.author = (char *)malloc(sizeof(50));
	myLib->collection.subject = (char *)malloc(sizeof(50));
	fscanf(fPtr,"%s%s%s",myLib->collection.title,myLib->collection.author,myLib->collection.subject);
	newPtr = malloc(sizeof(lib));
	if (newPtr != NULL)
	{
		newPtr->collection = myLib->collection;
		newPtr->next = NULL;
		while (currentPtr != NULL)
		{
			previousPtr = currentPtr;
			currentPtr = currentPtr->next;
		}
		if (previousPtr == NULL)
		{
			newPtr->next = *sPtr;
			*sPtr = newPtr;
		}
		else
		{
			previousPtr->next = newPtr;
			newPtr->next = currentPtr;
		}
	}
	else
	{
		puts("No memory available.\n");
	}
}

Code:

#include <stdio.h>#include <stdlib.h>
#include <string.h>

Your "#include" are wrong arranged.



Better:

Code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

If correct no warnings but nevertheless it will not run:



Also gcc -Wall -pedantic . . . shows no warnings or errors. Something is absolute wrong . . . but what?

Originally Posted by laserlight

I suggest that you get rid of this typedef:

Code:

typedef lib *libPtr;

It isn't wrong in itself, but generally a typedef of a pointer can make it more confusing to reason about the pointer, . . .

Now I have seen my mistake: the file "library.txt" was missing. But with it it won't work still.

"library.txt"

Programming Books
The Wait Group
Computer science

Maybe the reason for that is was @laserlight wrote.