Question

May I just ask why this piece of code is resulting to a segmentation fault. I’m trying to get input from a text file and I can’t figure out what is the problem.

using namespace std; 
using namespace cv;

int main()
{
    char str[50];
    FILE *trainfile;
    int k, n, maxval1, maxval2, classnum;
    char dataArray[n][3];

    trainfile = fopen("training.txt", "r+");

    if(trainfile == NULL){
        perror("Cannot open file.\n");
    }else{
        while(!feof(trainfile)){
            fscanf(trainfile, "%s", str);       
        }
    }
    fclose(trainfile);

    return 0;
}

Answer 1

One problem is that your buffer might not be big enough.

You should get the size of the file first, then make a dynamic buffer of that size, and then finally read the file.

fseek(trainfile,0,SEEK_END); //Go to end
int size = ftell(trainfile); //Tell offset of end from beginning
char* buffer = malloc(size); //Make a buffer of the right size

fseek(ftrainfile,0,SEEK_SET); //Rewind the file

//Read file here with buffer