CODEWITHSUNDEEP
c++
porfavorinho
porfavorinho

Reputation: 23

C++ - Opening text files sequentially

I have hundreds of .txt files ordered by number: 1.txt, 2.txt, 3.txt,...n.txt. In each file there are two columns with decimal numbers. I wrote an algorithm that does some operations to one .txt file alone, and now I want to recursively do the same to all of them. This helpful question gave me some idea of what I'm trying to do. Now I'm trying to write an algorithm to read all of the files:

#include <iostream>
#include <fstream>
#include <string>
using namespace std;
int main () 
{
int i, n;
char filename[6];
double column1[100], column2[100];
for (n=1;n=200;n++)
{
sprintf(filename, "%d.txt", n);
ifstream datafile;
datafile.open(filename);
    for (i=0;i<100;i++)
    {
    datafile >> column1[i] >> column2[i];
    cout << column1[i] << column2[i];
    }
datafile.close();
}
return 0;
}

What I think the code is doing: it is creating string names from 1.txt till 200.txt, then it opens files with these names. For each file, the first 100 columns will be associated to the arrays column1 and column2, then the values will be shown on the screen. I don't get any error when compiling it, but when I run it the output is huge and simply won't stop. If i set the output to a .txt file it reaches easily some Gb! I also tried decreasing the loop number and reduce the numbers of columns (to 3 or so), but I till get an infinite output. I would be glad if someone could point the mistakes I'm doing in the code... I am using gcc 5.2.1 with Linux. Thanks!

Upvotes: 1

Views: 267

Answers (2)

Marinos K
Marinos K

Reputation: 1829

If all your files are in the same directory, you could also use boost::filesystem, e.g.:

auto path = "path/to/folder";
std::for_each(boost::filesystem::directory_iterator{path},
        boost::filesystem::directory_iterator{},
        [](boost::filesystem::directory_entry file){
            // test if file is of the correct type
            // do sth with file
        });

I think this is a cleaner solution.

Upvotes: 0

MikeCAT
MikeCAT

Reputation: 75062

  • 6-element array is too short to store "200.txt". It must be at least 8 elements.
  • The condition n=200 is wrong and is always true. It should be n<=200.

Upvotes: 3

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