How can I copy a directory using Boost Filesystem

问题:

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.

回答1:

bool copyDir(
    boost::filesystem::path const & source,
    boost::filesystem::path const & destination
)
{
    namespace fs = boost::filesystem;
    try
    {
        // Check whether the function call is valid
        if(
            !fs::exists(source) ||
            !fs::is_directory(source)
        )
        {
            std::cerr << "Source directory " << source.string()
                << " does not exist or is not a directory." << '\n'
            ;
            return false;
        }
        if(fs::exists(destination))
        {
            std::cerr << "Destination directory " << destination.string()
                << " already exists." << '\n'
            ;
            return false;
        }
        // Create the destination directory
        if(!fs::create_directory(destination))
        {
            std::cerr << "Unable to create destination directory"
                << destination.string() << '\n'
            ;
            return false;
        }
    }
    catch(fs::filesystem_error const & e)
    {
        std::cerr << e.what() << '\n';
        return false;
    }
    // Iterate through the source directory
    for(
        fs::directory_iterator file(source);
        file != fs::directory_iterator(); ++file
    )
    {
        try
        {
            fs::path current(file->path());
            if(fs::is_directory(current))
            {
                // Found directory: Recursion
                if(
                    !copyDir(
                        current,
                        destination / current.filename()
                    )
                )
                {
                    return false;
                }
            }
            else
            {
                // Found file: Copy
                fs::copy_file(
                    current,
                    destination / current.filename()
                );
            }
        }
        catch(fs::filesystem_error const & e)
        {
            std:: cerr << e.what() << '\n';
        }
    }
    return true;
}

Usage:

copyDir(boost::filesystem::path("/home/nijansen/test"), boost::filesystem::path("/home/nijansen/test_copy")); (Unix)

copyDir(boost::filesystem::path("C:\\Users\\nijansen\\test"), boost::filesystem::path("C:\\Users\\nijansen\\test2")); (Windows)

As far as I see, the worst that can happen is that nothing happens, but I won't promise anything! Use at your own risk.

Please note that the directory you're copying to must not exist. If directories within the directory you are trying to copy can't be read (think rights management), they will be skipped, but the other ones should still be copied.

Update

Refactored the function respective to the comments. Furthermore the function now returns a success result. It will return false if the requirements for the given directories or any directory within the source directory are not met, but not if a single file could not be copied.

回答2:

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).

回答3:

Since C++17 you don't need boost for this operation anymore as filesystem has been added to the standard.

Use std::filesystem::copy

#include <exception>
#include <filesystem>
namespace fs = std::filesystem;

int main()
{
    fs::path source = "path/to/source/folder";
    fs::path target = "path/to/target/folder";

    try {
        fs::copy(source, target, fs::copy_options::recursive);
    }
    catch (std::exception& e) { // Not using fs::filesystem_error since std::bad_alloc can throw too.
        // Handle exception or use error code overload of fs::copy.
    }
}

See also std::filesystem::copy_options.

回答4:

This is a non-Boost version I'm using based on Doineann's code. I'm using std::filesystem but couldn't use a simple fs::copy(src, dst, fs::copy_options::recursive); because I wanted to filter which files are copied by file extension inside the loop.

void CopyRecursive(fs::path src, fs::path dst)
{
    //Loop through all the dirs
    for (auto dir : fs::recursive_directory_iterator(src))
    {
        //copy the path's string to store relative path string
        std::wstring relstr = dir.path().wstring();

        //remove the substring matching the src path
        //this leaves only the relative path
        relstr.erase(0, std::wstring(src).size());

        //combine the destination root path with relative path
        fs::path newFullPath = dst / relstr;

        //Create dir if it's a dir
        if (fs::is_directory(newFullPath))
        {
            fs::create_directory(newFullPath);
        }

        //copy the files
        fs::copy(dir.path(), newFullPath, fs::copy_options::recursive | fs::copy_options::overwrite_existing);
    }
}

relstr.erase(0, std::wstring(src).size()); is a working Boost-less replacement for the boost::replace_first() call used in the other answer