So I just started learning how to use file-streams in C & decided to attempt a question which is to do with library management in C, however I am currently encountering some problems and feel like I need some help/advice. Basically, my file name is libraryy.txt, I want to delete a book that I have inserted into my libraryy.txt file. When I enter the book's title into my compiler's output screen, I am expecting the compiler to read from my file (libraryy.txt) & delete that particular book's title, author & subject. However when I run my program, it doesn't seem to delete anything from my libraryy.txt file.

/*Data structures that the question wants me to use:*/
struct book{
 char *title;
 char *author;
 char *subject;
};
struct library {
    struct book collection;
    int num_books;
    struct library *next;
};
struct library* head;
struct book collection;
struct book *aPtr;
struct library aCollection;
struct library *aaPtr;

/*Below is my deleteBook function which I'm having a problem with*/
void deleteBook(struct library* thislib){
    //How to define library here?
    FILE *cfPtr, *cfPtr1;
    int j, found=0;
    char stitle[MAX];
    cfPtr = fopen("libraryy.txt", "r");
    cfPtr1 = fopen("temp.txt", "w");
    printf("Enter book title to delete:\n");
    scanf("%s", stitle);
    /*I'm confused on what I should be adding beside the '&' operator in the brackets of my 'while' loop*/
    while(fread(&thislib->collection, sizeof(struct library),1,cfPtr)){
        if(strcmp(stitle, thislib->collection.title)==0){
            found = 1;
        }
        else
            fwrite(&thislib->collection, sizeof(library), 1, cfPtr);
    }
    fclose(cfPtr);
    fclose(cfPtr1);
    if (found){
        cfPtr1 = fopen("temp.txt", "r");
        cfPtr = fopen("libraryy.txt", "w");
        while(fread(&thislib->collection, sizeof(library),1,cfPtr1)){ 
            fwrite(&thislib->collection, sizeof(library),1,cfPtr);
        }
        fclose(cfPtr);
        fclose(cfPtr1);
    }
}
 /*Other irrelevant functions which I did not include here like insertBook().....*/
/*Main function*/
int main (void){
   FILE *cfPtr;
/*Didn't include the whole coding to avoid the lengthiness of this question*/

Regarding the data structures provided that we have to use as it is a pre-requisite of the question as shown and defined in the code, I want to add that it seems that the 'library' data structure is supposed to access the 'book' data structure & the elements in it, so that it will allow me to delete the book (& its author, title as well as subject) from the file (libraryy.txt) when I enter the title of the book in my compiler screen.) Due to the question providing the data structure to me in that way, I am practically confused on how to access one data structure from another data structure, hence I'm not so sure on what to include beside the '&' operator in the while loop brackets as shown below for fread... is this how you do it, as shown in my code above? Also how do I define my library in the deleteBook() function?

posted over 2 years ago

CC BY-SA 4.0

2y ago by Alexei‭

dumplings‭

51 reputation 9 0 -25 31