Read multiple files by passing them in argv[1] - c++

Question

This might be a basic question, but I am new to C++, so I would appreciate your understanding.
What I am trying to do is to read files from a folder and pass one of them at a time in argv[1], get some results from that file, write them in an output file specified in argv[2], then the same for the next file, and so on.
I guess it has something to do with pointers but I am not sure how to fix this.
Thank you for any input!
Here is what I have so far:
vector<string> getFilenames(string folder)
{
vector<string> names;
string search_path = folder + "/*.*";
WIN32_FIND_DATA fd;
HANDLE hFind = ::FindFirstFile(search_path.c_str(), &fd);
if (hFind != INVALID_HANDLE_VALUE) {
do {
// read all (real) files in current folder
// , delete '!' read other 2 default folder . and ..
if (!(fd.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY)) {
names.push_back(fd.cFileName);
}
} while (::FindNextFile(hFind, &fd));
::FindClose(hFind);
}
return names;
}
int main(int argc, char **argv) {
ofstream fileout(argv[2], ios::out | ios::app);
int a, b, c;
vector<string> filenames = getFilenames("folder path");
istringstream iss;
for (int i = 0; i < filenames.size(); i++) {
iss.str(filenames[i]);
iss >> argv[1];
if (readFile(a, b, c, argv[1]) == 0) {
/* do something */
}
}
fileout.close();
return 0;
}

Answer 1

I want to complete #Florian Klemme but I cannot comment.
There is a little example of how to iterate through command line parameters :
int main(int argc, char **argv)
{
for (auto i = int{0}; i < argc; ++i) {
// do something with argv[i];
}
}

Answer 2

I'm not exactly sure what your problem is but maybe this little example can help as a starting point. It shows how you can
Iterate though files in a directory (you need C++17 though)
Read some number from a file
Write to another file
Hopefully you can add the rest with no problem. :)
#include <filesystem>
#include <fstream>
#include <iostream>
#include <string>
namespace fs = std::filesystem;
int main(int argc, char **argv) {
std::string input_dir = argv[1];
std::string output_file = argv[2];
std::ofstream out(output_file);
// Iterate over files in directory
for(auto& file : fs::directory_iterator(input_dir)) {
std::ifstream in(file.path());
// In this example, read a integer number from the current file
if (int i; in >> i) {
std::cout << "Read " << i << " from " << file << std::endl;
// ... and write it to the output file.
out << i << std::endl;
}
}
}