如何使用标准计数目录中的文件数？ [英] How to count the number of files in a directory using standard?

问题描述

预计在2017年推出的新标准将添加 std :: filesystem 。使用它，如何计算目录中文件（包括子目录）的数量？

The new standard expected for 2017 adds std::filesystem. Using it, how can I count the number of files (including sub-directories) in a directory?

我知道我们可以做到：

std::size_t number_of_files_in_directory(std::filesystem::path path)
{
    std::size_t number_of_files = 0u;
    for (auto const & file : std::filesystem::directory_iterator(path))
    {
        ++number_of_files;
    }
    return number_of_files;
}

但这似乎有些过分。是否存在更简单，更快速的方法？

But that seems overkill. Does a simpler and faster way exist?

推荐答案

我认为不存在一种轻松获取目录中文件数量的方法，但是您可以使用 std :: distance 而不是手写循环来简化代码：

I do not think that a way to easily get amount of files in directory exist, but you can simplify your code by using std::distance instead of handwritten loop:

std::size_t number_of_files_in_directory(std::filesystem::path path)
{
    using std::filesystem::directory_iterator;
    return std::distance(directory_iterator(path), directory_iterator{});
}

您可以通过使用<获得仅实际文件数或应用任何其他过滤器code> count_if 代替：

std::size_t number_of_files_in_directory(std::filesystem::path path)
{
    using std::filesystem::directory_iterator;
    using fp = bool (*)( const std::filesystem::path&);
    return std::count_if(directory_iterator(path), directory_iterator{}, (fp)std::filesystem::is_regular_file);
}

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