Namespaces
Variants

    std::filesystem::space_info

    From cppreference.com
     
    C++
     
    Filesystem library
    Classes
    Functions
    File types
     
    Defined in header <filesystem>
    struct space_info { std::uintmax_t capacity; std::uintmax_t free; std::uintmax_t available; };
    		 (since C++17)
    See More

    Represents the filesystem information as determined by filesystem::space.

    Member objects

    capacity
    		 total size of the filesystem, in bytes
    (public member object)
    free
    		 free space on the filesystem, in bytes
    (public member object)
    available
    		 free space available to a non-privileged process (may be equal or less than free)
    (public member object)

    Non-member functions

    (C++20)
    		 compares two space_infos
    (function)

    operator==(std::filesystem::space_info)

    friend bool operator==( const space_info&, const space_info& ) = default;
    		 (since C++20)

    Checks if capacity, free and available of both arguments are equal respectively.

    This function is not visible to ordinary unqualified or qualified lookup, and can only be found by argument-dependent lookup when std::filesystem::space_info is an associated class of the arguments.

    The != operator is synthesized from operator==.

    Example

    Run this code
    #include <cstdint>
#include <filesystem>
#include <iostream>
#include <locale>

std::uintmax_t disk_usage_percent(const std::filesystem::space_info& si,
                                  bool is_privileged = false) noexcept
{
    if (constexpr std::uintmax_t X(-1);
        si.capacity == 0 || si.free == 0 || si.available == 0 ||
        si.capacity == X || si.free == X || si.available == X
    )
        return 100;

    std::uintmax_t unused_space = si.free, capacity = si.capacity;
    if (!is_privileged)
    {
        const std::uintmax_t privileged_only_space = si.free - si.available;
        unused_space -= privileged_only_space;
        capacity -= privileged_only_space;
    }
    const std::uintmax_t used_space{capacity - unused_space};
    return 100 * used_space / capacity;
}

void print_disk_space_info(auto const& dirs, int width = 14)
{
    (std::cout << std::left).imbue(std::locale("en_US.UTF-8"));

    for (const auto s : {"Capacity", "Free", "Available", "Use%", "Dir"})
        std::cout << "│ " << std::setw(width) << s << ' ';

    for (std::cout << '\n'; auto const& dir : dirs)
    {
        std::error_code ec;
        const std::filesystem::space_info si = std::filesystem::space(dir, ec);
        for (auto x : {si.capacity, si.free, si.available, disk_usage_percent(si)})
            std::cout << "│ " << std::setw(width) << static_cast<std::intmax_t>(x) << ' ';
        std::cout << "│ " << dir << '\n';
    }
}

int main()
{
    const auto dirs = {"/dev/null", "/tmp", "/home", "/proc", "/null"};
    print_disk_space_info(dirs);
}

    Possible output: 

    │ Capacity       │ Free           │ Available      │ Use%           │ Dir            
│ 84,417,331,200 │ 42,732,986,368 │ 40,156,028,928 │ 50             │ /dev/null
│ 84,417,331,200 │ 42,732,986,368 │ 40,156,028,928 │ 50             │ /tmp
│ -1             │ -1             │ -1             │ 100            │ /home
│ 0              │ 0              │ 0              │ 100            │ /proc
│ -1             │ -1             │ -1             │ 100            │ /null

    See also

    (C++17)
    		 determines available free space on the file system
    (function) [edit]