Thread: Problem reading in Text File

A couple of problems:

1. Do not typedef pointers, you have been told that before. It is extremely poor programming practice.
2. You stuff array is local to your function and goes out of scope when your function exits. Thus leaving your node pointing to invalid memory.
3. Why would sscanf effect where your file pointer was. You have it reading from your area buffer, which you never put anything into, and then outputting into your area value of your node. How does that change the file pointer? Here is sscanf explanation.

Code:

typedef struct Item
{
    char *name;
    int area;
    struct Item *nextPtr;
} Item;

typedef Item *Ptr;

...

Ptr newPtr;

...

newPtr = malloc(sizeof(Ptr));

That certainly doesn't look right... you mean sizeof(*newPtr) instead?

Originally Posted by voidpain()

Is there any way I could replace the sscanf with an fgets, or will fgets not be able to store the number into an integer variable? Is there any way I could bump the file pointer forward otherwise?

I am not sure of your file layout, however normally you would just read the file in line by line using fgets into some buffer and then break that up with sscanf() to effectively parse the line. So something like this:

Code:

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

struct myNode{
	char name[30]; //note this isn't a pointer
	int number;
};

//just used to make our file
void createFile(void);

int main(void){

	//used for file line input
	char inputBuffer[100]={0};
	FILE* myFile;
	int current=0;
	
	//I am using an array but this would be your linked list
	struct myNode myNodeArray[5];
	//---------------------
	
	//just makes our file to read in
	createFile();
	
	//open our file
	myFile = fopen("example.txt", "r");
	
	if(myFile){
		//read our file in line by line
		while(fgets(inputBuffer, sizeof(inputBuffer), myFile) && current < 5){
			//break up our line into our structure
			sscanf(inputBuffer,"%s %d", myNodeArray[current].name, &myNodeArray[current].number);
			current++;
		}
		fclose(myFile);
	}
	//printf our results
	for(int i = 0; i < current; i++){
		printf("%s %d\n", myNodeArray[i].name , myNodeArray[i].number);
	}

	getchar();
	return (0);
}
void createFile(){

	FILE* myfile = fopen("example.txt", "w");
	if(myfile){
		fprintf(myfile, "John 30\n");
		fprintf(myfile, "Joe 20\n");
		fprintf(myfile, "Bob 15\n");
		fclose(myfile);
	}
}

Originally Posted by voidpain()

Is there any way I could replace the sscanf with an fgets, or will fgets not be able to store the number into an integer variable? Is there any way I could bump the file pointer forward otherwise?

Maybe you would find fscanf() more useful.

Also, I would like to note that unless there is any reason your files need to be human readable, e.g. txt files, you really should look at just making binary files for this. I am assuming you are making something of a game here, so in that case it would greatly simplify how you manages these files and load your data.

Just search this forum and the internet for "Random Access Files". By doing this you will have many advantages such as reading and writing directly from/to a structure and being able to jump around in your data file, hence "random access".