Thread: homework (reading and writing a file)

I have a homework problem that I could really use some help on. Here are the directions: write a program to read a set of scores from a text file, count the scores over 90, copy the scores over 90 to a new file and print the number of scores over 90 to the monitor.

Code:

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

int newlist(int score);//function declaration

FILE* spData;// file to read from
FILE* spnewList;

int score;//global variable dec.
char name;

int main()//main
{

int below = 0; //local declarations
int count = 0;


 printf("This program will print scores over 90%\n");

spData = fopen("TextFile1.txt", "r");
    if (!spData)
        {
        printf("Could not open file \a\n");
        exit (101);
        }//if open fails
        
while (!EOF)
    fscanf(spData, " %d", &score);

        if (score > 90)
        {    count++;}
        else
            {below++;}

printf("The number of scores above 90% are %d\n", count);
printf("The number of scores below 90% are %d\n", below);

newlist(score);


    return 0;
}//main
/*=================newlist==================*/
int    newlist(int score)//writes info to new file
{
spnewList = fopen("Gradelist.txt", "w");//creates new file

    if (score > 90) 
        fprintf(spnewList, " %d", score);
    
    return 1;

}//newlist

I hope I did this correctly. I thought that this would be pretty easy but I can't see my problem. please help.

I guess I should add that it does compile but doesn't open the file.

Is the file in the same location as the executable? If not, well then that's the problem.

Code:

while (!EOF)
    fscanf(spData, " %d", &score);

        if (score > 90)
        {    count++;}
        else
            {below++;}

Using EOF is bad juju, and you're doing so incorrectly anyway. And the only thing in that while loop is the fscanf. If you want more than the line following a control statement like while to be executed, you need to use braces around that code ( {} ).

Global Variables Are Bad. Please move the definitions to main and pass them to any functions that need them.

Code:

while (!EOF)
    fscanf(spData, " %d", &score);

That is not the loop you want. EOF is probably defined as -1 on your system, and thus !EOF is false, so the loop never executes. You shouldn't use the EOF marker for loop control anyway, even if you use the feof function: Cprogramming.com FAQ > Why it's bad to use feof() to control a loop.

Read up on fscanf and control your loop using the return value of fscanf.

Oh, and you have to use %% in a printf string to get an actual percent sign to show up, otherwise it thinks the following character is a format specifier (like %d, %c, etc).

anduril462 "Global variables are bad" - yeah, bad habit, I pass them in the functions anyway. I'll move them down. thanks.

Ok. I have updated my code and read the link of feof. I have made all of the changes except the while loop. I get that fgets() is better to read whole lines of code, but I'm not grasping how to know when to stop. any help would be greatly appreciated.

I noticed a few more things:

1. You need to check every score you read to see if it's over 90, so that belongs in your read loop along with incrementing your counts and writing it to file.
2. Your newlist file opens Gradelist.txt every time but never closes it. You can open it once at the beginning of main and close it at the end. You can probably ditch the newlist function and move all your code into main.
3. You also need to close TextFile1.txt when you're done.

Posting your new code would be helpful. Also, you should read the docs on fscanf. You will find it easier than fgets, and you wont have to worry about possibly chopping a number in half with fgets if your buffer is too small for the line in your text file.

Code:

while (fscanf("%d", &score) != ?) {
}

Figure out what fscanf should return if it worked right and put it where the ? is.

Code:

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

FILE* spData;// file to read from
FILE* spGradelist;

int main()//main
{

int below = 0; //local declarations
int count = 0;
int score;

 printf("This program will print scores over 90%\n");

spGradelist = fopen("Gradelist.txt", "w");
spData = fopen("TextFile1.txt", "r");
    if (!spData)
        {
        printf("Could not open file \a\n");
        exit (101);
        }//if open fails
        
while ()
   { fscanf(spData, " %d", &score);

        if (score > 90)
        { fprintf(spGradelist, "%d", score);//creates new file
			count++;}
        else
            {below++;}
}
printf("The number of scores above 90%% are %d\n", count);
printf("The number of scores below 90%% are %d\n", below);



fclose(spData);
fclose(spGradelist);
return 0;
}//main

here is the updated code, it my while loop is incomplete but everything else seems fine. I'm still looking into fscanf.

ok, would it be stupid to put "1000" at the end of the list and when score is != 1000.

here is my textfile1
Billy 98
Charlie 72
Megan 89
Mike 96
Tim 91
Adrian 79
Rob 82
Mark 91

//it is just a generic list, it can be anything

Your loop isn't quite what I had in my previous post. You need to put fscanf in the loop condition.

Using a value like 1000 to mark the end of list is not stupid, though it's arguably not the best solution here. What you suggested is called a sentinel value, and is common in things like linked lists, where one uses NULL to mark the end of the list. For integer data, like scores, a common value might be -1 since that's not a valid score under most circumstances. But keep after that fscanf, it's the best method for your situation. Here's the documentation for scanf, pay particular attention to the "Return Value" section: scanf(3) - Linux manual page.

but does't open the file.

So you mean you're seeing:

printf("Could not open file \a\n");

Because if you aren't, then it is opening the file. And if it's not opening the file (because you are seeing that message) then your file doesn't exist or you don't have permissions to open it, etc. None of which has anything to do with your loop.


Quzah.

If it fails to open the file, then you can ignore everything else in your code from that point on. The problem is that the file you are trying to access either doesn't exist, or you don't have permission to access it. (Or in the case of writing a new one, you can't create a new file there for some reason.)


Quzah.