File Input

This is a discussion on File Input within the C Programming forums, part of the General Programming Boards category; I have a question regarding reading input from a file. The input file (input.txt): Code: 8 9 2.5 10 5 ...

  1. #1
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    Nov 2007
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    5

    File Input

    I have a question regarding reading input from a file.

    The input file (input.txt):
    Code:
    8 9 2.5
    10 5 2.6
    7 15 9.5
    0 0 0
    1
    1 8
    My program:
    Code:
    #include <stdio.h>
    
    #define MAX_TBL_SIZE 30
    
    int main()
    {
        FILE *ifp;
        
        char name[10];
        int index = 0;
        int ind2;
        int id[MAX_TBL_SIZE], stock[MAX_TBL_SIZE];
        float price[MAX_TBL_SIZE];
        
        // Reads user input for filename. 10 character long string. Guaranteed to be correct filename.
        printf("Enter the name of the input file:\n");
        scanf("&#37;s", name);
        printf("\n");
    
        // Opens the filename entered
        ifp = fopen(name, "r");
        
        // Adds variables from file into specified arrays
        while(id[index] != 0 && stock[index] !=0 && price[index] != 0.0)
        {
                        fscanf(ifp, "%d", &id[index]);
                        fscanf(ifp, "%d", &stock[index]);
                        fscanf(ifp, "%f", &price[index]);
                        
                        index++;
        }
        
         
        // Prints current index value
        printf("DEBUGGER: INDEX = %d\n", index);
        
        // Prints each value of array id untill it reaches the index vaule
        for (ind2 = 0; ind2 < index; ind2++)
        {
            printf("DEBUGGER: id[%d] = %d", ind2, id[ind2]);
            printf("\n");
        }
        
        // Same as above, except for stock array
        for (ind2 = 0; ind2 < index; ind2++)
        {
            printf("DEBUGGER: stock[%d] = %d", ind2, stock[ind2]);
            printf("\n");
        }
        
        // Repeated for price array
        for (ind2 = 0; ind2 < index; ind2++)
        {
            printf("DEBUGGER: price[%d] = %.2f", ind2, price[ind2]);
            printf("\n");
        }
        
    
         // Shows current location in file
         fscanf(ifp, "%d", &num);
         printf("CURRENT LOCATION fscanf: %d\n", num);
    
        // Closes file
        fclose(ifp);
    
        system("PAUSE");
        return 0;
    }
    What I want my program to do is to add these variables to 3 different arrays, but stop once it reaches the three zero string (0 0 0).

    When it compiles, it seems my index value is stopping too soon. Each time it only seems to accumulate to 2 before stopping, rather than stopping once it reaches the marker.

    Any ideas on what is going on here?
    Last edited by Mcwaffle; 11-10-2007 at 01:24 AM.

  2. #2
    and the hat of int overfl Salem's Avatar
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    Your index++ means you're always comparing the junk in your arrays (which are uninitialised, so it's just random what happens), and not comparing the last 3 values read from the file.

    I would suggest reading the FAQ on how to use fgets() and sscanf()
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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