I am slowly learning C, but not very well. I have been reading over the countless topics and questions on reading and writing, but I have yet to be able to find anything that makes this all click for me.
I was given the following code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAX 100
struct YouTubeVideo {
char video_name[1024]; // YouTube video name
int ranking; // Number of viewer hits
char url[1024]; // YouTube URL
};
struct YouTubeVideo Collection[MAX];
int tail = 0;
//-- Forward Declaration --//
void printall();
void insertion();
void branching(char option);
void menu();
int main()
{
char ch;
// TODO: Add code to load save data from file
printf("\n\nWelcome to CSE240: YouTube Classic Hits\n");
do {
menu();
fflush(stdin); // Flush the standard input buffer
ch = tolower(getchar()); // read a char, convert to lower case
branching(ch);
} while (ch != 'q');
return 0;
}
void menu()
{
printf("\nMenu Options\n");
printf("------------------------------------------------------\n");
printf("i: Insert a new favorite\n");
printf("p: Review your list\n");
printf("q: Save and quit\n");
printf("\n\nPlease enter a choice (i, p, or q) ---> ");
}
void branching(char option)
{
switch(option)
{
case 'i':
insertion();
break;
case 'p':
printall();
break;
case 'q':
// TODO: Add code to save data into a file
break;
default:
printf("\nError: Invalid Input. Please try again...");
break;
}
}
void insertion()
{
if(tail < MAX)
{
printf("\nWhat is the name of the video? (No spaces characters allowed)\n");
scanf("%s", Collection[tail].video_name);
printf("\nHow many viewer hits does this video have?\n");
scanf("%d", &Collection[tail].ranking);
printf("\nPlease enter the URL: ");
scanf("%s", &Collection[tail].url);
tail++;
}
else
{
printf("\nERROR: Your collection is full. Cannot add new entries.\n");
}
}
void printall()
{
int i;
printf("\nCollections: \n");
for(i = 0; i < tail; i++)
{
printf("\nVideo Name: %s", Collection[i].video_name);
printf("\nRanking (Hits): %d", Collection[i].ranking);
printf("\nURL: %s", Collection[i].url);
printf("\n");
}
}
I am suppose to write the code that will store the collection into a file and the likewise right the code that will load the file and read from it.
Thanks to a fairly helpful TA I was able to formulate the following code for each
void store()
{
FILE * fileName;
fileName = fopen ( "Ranking.dbm" , "wb" );
fwrite ( Collection, sizeof(struct YouTubeVideo), MAX, fileName);
fclose (fileName);
}
and
void read()
{
FILE *fileName;
fileName = fopen("ranking.dbm", "rb");
if (fileName != NULL){
fread ( Collection, sizeof(struct YouTubeVideo), MAX, fileName);
}
else {
printf("ERROR");
}
}
I believe these each to function but the real problem is I don’t think I quite understand how and I believe that since I dont even know how they function, I dont know how to use them in the code.
I added both methods to the given code and came up with this:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#define MAX 100
struct YouTubeVideo {
char video_name[1024]; // YouTube video name
int ranking; // Number of viewer hits
char url[1024]; // YouTube URL
};
struct YouTubeVideo Collection[MAX];
int tail = 0;
//-- Forward Declaration --//
void printall();
void insertion();
void branching(char option);
void menu();
void store();
void read();
int main()
{
char ch;
read();
printf("\n\nWelcome to CSE240: YouTube Classic Hits\n");
do {
menu();
fpurge(stdin); // Flush the standard input buffer
ch = tolower(getchar()); // read a char, convert to lower case
branching(ch);
} while (ch != 'q');
return 0;
}
void menu()
{
printf("\nMenu Options\n");
printf("------------------------------------------------------\n");
printf("i: Insert a new favorite\n");
printf("p: Review your list\n");
printf("q: Save and quit\n");
printf("\n\nPlease enter a choice (i, p, or q) ---> ");
}
void branching(char option)
{
switch(option)
{
case 'i':
insertion();
break;
case 'p':
printall();
break;
case 'q':
store();
break;
default:
printf("\nError: Invalid Input. Please try again...");
break;
}
}
void insertion()
{
if(tail < MAX)
{
printf("\nWhat is the name of the video? (No spaces characters allowed)\n");
scanf("%s", Collection[tail].video_name);
printf("\nHow many viewer hits does this video have?\n");
scanf("%d", &Collection[tail].ranking);
printf("\nPlease enter the URL: ");
scanf("%s", &Collection[tail].url);
tail++;
}
else
{
printf("\nERROR: Your collection is full. Cannot add new entries.\n");
}
}
void printall()
{
int i;
printf("\nCollections: \n");
for(i = 0; i < tail; i++)
{
printf("\nVideo Name: %s", Collection[i].video_name);
printf("\nRanking (Hits): %d", Collection[i].ranking);
printf("\nURL: %s", Collection[i].url);
printf("\n");
}
}
void store()
{
FILE * fileName;
fileName = fopen ( "Ranking.dbm" , "wb" );
if (fileName != NULL)
{
fwrite ( Collection, sizeof(struct YouTubeVideo), MAX, fileName);
fclose (fileName);
}
else {
perror("Following error occurred(): ");
}
}
void read()
{
FILE *fileName;
fileName = fopen("Ranking.dbm", "rb");
if (fileName != NULL)
{
fread ( Collection, sizeof(struct YouTubeVideo), MAX, fileName);
fclose(fileName);
}
else {
perror("Following error occurred with fopen(): ");
}
}
Now I am sure anyone who has read this has probably already face palmed themselves cause they see the problem, but I do not. The code does not create the file to write to and likewise it has nothing to read from so I cant even begin to see what is wrong with that.
Now I am not looking for a given answer, but I would really like to know what it is I am doing incorrectly, what concepts I appear to not understand, and how I can go about fixing these. I have done a few hours of research on this already and I realize it is elementary, but I really would like a hand in learning. Its frustrating spending hours on a topic that the professor said should only take a couple of hours to complete at most.
Minor: Make sure to check the return values for things like fopen, fread, fwrite etc. more often.
Mild: You’ve got a potential typo in the filename (some operating systems have case-sensitive file names)
Severe: read() doesn’t set up a value for tail… 🙂