CODEWITHSUNDEEP
c++fileinput
Peter Nicolai Knudsen
Peter Nicolai Knudsen

Reputation: 37

How to run a c++ program multiple times with different input files?

I'm new to C++ and writing my master thesis and would really appreciate any help I can get!

I have a program that reads a txt file, then does a bunch of calculations, and returns a new txt file. The thing is that I want to run this program for 100+ different input files. Now I have to change the name of the input file in the code, but I would like to have it run for all the input files in my folder by itself.

I am using Visual Studio, but with little C++ experience.

Thanks :)

Upvotes: 1

Views: 2730

Answers (4)

ObliteratedJillo
ObliteratedJillo

Reputation: 5156

See this snippet. Since you are using MSCV, you need to enable MFC in configuration for this console application. Also add #include "afx.h" in #include "stdafx.h" where CFileFind is defined. PopulateFromFolder() should auto load the files into the vector files.

#include "stdafx.h"
#include <iostream>
#include <string>
#include <fstream>
#include <vector>   

using namespace std;

void PopulateFromFolder(string path, vector<string>& files)
{
    CFileFind   finder;
    CString fileName;
    fileName.Format(L"%s*.*", CString(path.c_str()));
    BOOL bOk = finder.FindFile(fileName);
    while (bOk)
    {
        bOk = finder.FindNextFile();

        if (finder.IsDots())
        {
            continue;
        }
        if (!finder.IsDirectory())
        {
            CString strFileName = finder.GetFileName();
            files.push_back(CStringA(strFileName).GetString());
        }
    }
    finder.Close();
}

int main()
{
    vector<string> files;
    string path = "D:\\MyFolder\\";
    PopulateFromFolder(path, files);

    auto a = path + files[0];
    int i = 0;
    while (i< files.size()-1)
    {
        cout << "processing " << files[i + 1] << endl;
        ifstream fs(path+files[i++]);
        if (fs.is_open())
        {
            //do something
        }
        fs.close();
    }
    return 0;
}

Output:

enter image description here

Upvotes: 1

mks
mks

Reputation: 76

You can try to use std::experimental::filesystem (http://en.cppreference.com/w/cpp/experimental/fs). I guess that directory_iterator from this library can be useful for you - it allows you to iterate over all files in a given directory. Have a look at the example provided in the documentation: http://en.cppreference.com/w/cpp/experimental/fs/directory_iterator. However, you have to make sure that you are compiling your code with a new standard (C++ 17).

Another way is to make for example a separate file containing a list of the names of all files that you want to work on. Then, you can read this list and for every file do what you need.

Upvotes: 0

Peter
Peter

Reputation: 98

Using bash you can run them using:

$ for file in /Data/*.txt; do /path/your_program $file; done

Upvotes: 1

NuPagadi
NuPagadi

Reputation: 1440

You can define format for your input files names and put then into some directory. For example,

Input1.txt
Input2.txt
...
Input111.txt

Then use some kind of for loop:

for(int i = 1; i <= 111; ++i)
{
    ifstream file("Input" + std::to_string(i) + ".txt");
    if (file.is_open())
        Operate(file);
}

If you don't know the exact number of files, you can check whether the file was openen by is_open() method. This way files with some numbers can be absent. You just loop for some max possible input file id.

This was a solution which doesn't require any dependencies. But if you don't mind it, you actually may consider Boost.Filesystem. Here is an example.

Upvotes: 0

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