C++17 in Detail: A Deep Dive/

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Demo Example for Path Object

Demo Example for Path Object

This lesson shows a demo code sample that we are going to discuss in the upcoming lessons. The code basically displays files in a given directory.

We'll cover the following...

Demo

Instead of exploring the library piece by piece at the start, let’s see a demo example: displaying basic information about all the files in a given directory (recursively). This should give you a high-level overview of how the library looks like.

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#include <filesystem>
#include <iomanip>  
#include <iostream>
namespace fs = std::filesystem;
void DisplayDirectoryTree(const fs::path& pathToScan, int level = 0) {
    for (const auto& entry : fs::directory_iterator(pathToScan)) {
        const auto filenameStr = entry.path().filename().string();
        if (entry.is_directory()) {
            std::cout << std::setw(level * 3) << "" << filenameStr << '\n';
            DisplayDirectoryTree(entry, level + 1);
        }
        else if (entry.is_regular_file()) {
            std::cout << std::setw(level * 3) << ""<< filenameStr
                << ", size " << fs::file_size(entry) << " bytes\n";
        }
        else
            std::cout << std::setw(level * 3) << "" << " [?]" << filenameStr << '\n';
    }
}
int main(int argc, char* argv[]) {
    try  {
        const fs::path pathToShow{ argc >= 2 ? argv[1] : fs::current_path() };
        std::cout << "listing files in the directory: " 
                  << fs::absolute(pathToShow).string() << '\n';
        DisplayDirectoryTree(pathToShow);
    }
    catch (const fs::filesystem_error& err) {
        std::cerr << "filesystem error! " << err.what() << '\n';
    }
    catch (const std::exception& ex) {
        std::cerr << "general exception: " << ex.what() << '\n';
    }
}

Sample Outputs

We can run this program on a temp path D:\testlist and see the following output:

Running on Windows:

.\ListFiles.exe D:\testlist\
listing files in the directory: D:\testlist\
abc.txt, size 357 bytes
def.txt, size 430 bytes
ghi.txt, size 190 bytes
dirTemp
   jkl.txt, size 162 bytes
   mno.txt, size 1728 bytes
tempDir
   abc.txt, size 174 bytes
   def.txt, size 163 bytes
   tempInner
      abc.txt, size 144
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