How can I copy a directory using Boost Filesystem

Question

How can I copy a directory using Boost Filesystem? I have tried boost::filesystem::copy_directory() but that only creates the target directory and does not copy the contents

Answer 1

I see this version as an improved upon version of @nijansen's answer. It also supports the source and/or destination directories to be relative.

namespace fs = boost::filesystem;

void copyDirectoryRecursively(const fs::path& sourceDir, const fs::path& destinationDir)
{
    if (!fs::exists(sourceDir) || !fs::is_directory(sourceDir))
    {
        throw std::runtime_error("Source directory " + sourceDir.string() + " does not exist or is not a directory");
    }
    if (fs::exists(destinationDir))
    {
        throw std::runtime_error("Destination directory " + destinationDir.string() + " already exists");
    }
    if (!fs::create_directory(destinationDir))
    {
        throw std::runtime_error("Cannot create destination directory " + destinationDir.string());
    }

    for (const auto& dirEnt : fs::recursive_directory_iterator{sourceDir})
    {
        const auto& path = dirEnt.path();
        auto relativePathStr = path.string();
        boost::replace_first(relativePathStr, sourceDir.string(), "");
        fs::copy(path, destinationDir / relativePathStr);
    }
}

The main differences are exceptions instead of return values, the use of recursive_directory_iterator and boost::replace_first to strip the common part of the iterator path, and relying on boost::filesystem::copy() to do the right thing with different file types (preserving symlinks, for instance).