Thread: Segmentation fault

Hello All,

I'm new to C programming and have been set an assignment. We are to read in float values from a text file and insert them into two arrays, then perform certain manipulations to the stored values. I have managed to insert the data into separate arrays (one for each column), but when trying to sum together all the values, I end up with a segmentation fault - despite trying different variable types.

Can somebody please help me with this code? Below is the code so far and I've attached the text file.

Regards,

Paul.

Code:

/* 
 * File:   newmain.c
 * Author: paul
 *
 * Created on 09 February 2010, 19:37
 */

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

/*
 * 
 */
int main() {
    FILE *file;
    float col1[100000];
    float col2[100000];
    /* make sure it is large enough to hold all the data! */
    int i, j;
    long k;
    float sum;
    float average;

    file = fopen("/home/paul/assessment2_data.txt", "r");

    if (file == NULL) {
        printf("Error: can't open file.\n");
        return 1;
    } else {
        printf("File opened successfully.\n");

        i = 0;

        while (!feof(file)) {
            /* loop through and store the numbers into the array */
            fscanf(file, "%f\t%f", &col1[i], &col2[i]);
            i++;
        }
    }

    printf("Amount of numbers read: %d\n\n", i);
    printf("The numbers are:\n");

    printf("\nColumn 1:\n\n");
    for (j = 0; j < i; j++) { /* now print them out 1 by 1 */
        printf("%f\n", col1[j]);
    }
    printf("\nColumn 2:\n\n");
    for (j = 0; j < i; j++) {
        printf("%f\n", col2[j]);
    }

    sum = 0;
    average = 0;

    for (k = 0; k <= sizeof(col1); k++){
        printf("Loop number: %d\n", k);
        sum += col1[k];
    }
    printf("The sum of Column 1 is: %f", sum);

    fclose(file);
    return 0;
}

Thanks for your help Elysia - I realised it would be much easier to re-use the counter 'i' as this will have effectively 'counted' the number of elements into the array. I *think* this is problem solved... for now! Cheers, Paul.

OK - I've managed to resolve this issue, only to find another later down the line! When working out the minimum value stored within the two arrays I get an unexpected output for the first column of '0.000000' yet the code works for the second column. Here is my current code:

Code:

/*
 * File:   newmain.c
 * Author: Paul R. Smith
 *
 * Created on 09 February 2010, 19:37
 */

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

/*
 *
 */
int main() {
    FILE *file;
    float col1[100000];
    float col2[100000];
    /* make sure it is large enough to hold all the data! */
    int arr_ele, j, k, l, m, n, o, gotNum;
    float sum_col1, sum_col2;
    float average_col1, average_col2;
    float max_col1, max_col2, min_col1, min_col2;

    if ((file = fopen("/home/paul/assessment2_data.txt", "rt")) == NULL) {
        printf("\nError opening file\n");
        return 1;
    }
    arr_ele = 0;
    do {
        gotNum = 0;
        gotNum = fscanf(file, "%f%f", &col1[arr_ele], &col2[arr_ele]);
        if (gotNum > 1)
            printf("\n%f   %f", col1[arr_ele], col2[arr_ele]);
        arr_ele++;

    } while (gotNum > 1);

    printf("\nAmount of numbers read: %d\n\n", arr_ele);
    printf("The numbers are:\n");

    sum_col1 = 0;
    sum_col2 = 0;

    for (k = 0; k < arr_ele; k++) {
        sum_col1 += col1[k];
    }

    for (k = 0; k < arr_ele; k++) {
        sum_col2 += col2[k];
    }

    printf("The sum of Column 1 is: %f\n", sum_col1);
    printf("The sum of Column 2 is: %f\n", sum_col2);

    average_col1 = 0;
    average_col2 = 0;

    average_col1 = sum_col1 / arr_ele;
    average_col2 = sum_col2 / arr_ele;

    printf("The average of Column 1 is: %f\n", average_col1);
    printf("The average of Column 2 is: %f\n", average_col2);

    for (m = 0; m < arr_ele; m++) {
        if (col1[m] > max_col1) {
            max_col1 = col1[m];
        } else if (col1[m] < min_col1) {
            min_col1 = col1[m];
        }
    }

    for (m = 0; m < arr_ele; m++) {
        if (col2[m] > max_col2) {
            max_col2 = col2[m];
        } else if (col2[m] < min_col2) {
            min_col2 = col2[m];
        }
    }

    printf("The maximum value in Column 1 is: %f\n", max_col1);
    printf("The maximum value in Column 2 is: %f\n", max_col2);

    printf("The minimum value in Column 1 is: %f\n", min_col1);
    printf("The minimum value in Column 2 is: %f\n", min_col2);

    fclose(file);
    return 0;
}

The input text file remains the same as per my earlier post. I simply can't fathom out for why, any help greatly appreciated!

With all due respect, this may be "trivial" to you though I've only been programming for a few days! I do have a debugger and it runs without fail. You say they aren't initialised but I've now done this (correctly I hope!) and they're set to 0... still getting strange outputs. Thanks!

Thanks Salem,

I tried your suggested code but this resulted in my program only reading in 1 value from the text file?! I'm really quite confused now haha!

I slotted the if/else statement into the place of the do/while loop... I think I've done this wrong. Could you please show me how you intended then hopefully I'll get my head round this. I've spent far too long looking at the same code... my brain is frazzled!

Cheers,

Paul.

Thanks Elysia - I'll have a go at this now.

Salem - The full text file is attached above in an earlier post though here are 10 lines in any case:

Code:

2.67	2.464
2.393	1.228
2.167	0.657
5.047	2.033
7.993	2.169
7.917	1.249
4.874	1.66
4.384	2.166
5.355	2.896
4.505	2.637

There are no line spaces between rows. Cheers!

Thank you ever so much Salem, I understand now, much better the fgets() approach! Thanks also to Elysia for your comments!