NAME¶

std::filesystem::space - std::filesystem::space

Synopsis¶

Defined in header <filesystem>
std::filesystem::space_info space( const std::filesystem::path& p (1) (since C++17)
);
std::filesystem::space_info space( const std::filesystem::path& p, (2) (since C++17)
std::error_code& ec ) noexcept;

Determines the information about the filesystem on which the pathname p is located,
as if by POSIX statvfs.

Populates and returns an object of type filesystem::space_info, set from the members
of the POSIX struct statvfs as follows:

* space_info.capacity is set as if by f_blocks * f_frsize.
* space_info.free is set to f_bfree * f_frsize.
* space_info.available is set to f_bavail * f_frsize.
* Any member that could not be determined is set to
static_cast<std::uintmax_t>(-1).

The non-throwing overload sets all members to static_cast<std::uintmax_t>(-1) on
error.

Parameters¶

p - path to examine
ec - out-parameter for error reporting in the non-throwing overload

Return value¶

The filesystem information (a filesystem::space_info object).

Exceptions¶

Any overload not marked noexcept may throw std::bad_alloc if memory allocation
fails.

1) Throws std::filesystem::filesystem_error on underlying OS API errors, constructed
with p as the first path argument and the OS error code as the error code argument.
2) Sets a std::error_code& parameter to the OS API error code if an OS API call
fails, and executes ec.clear() if no errors occur.

Notes¶

space_info.available may be less than space_info.free.

Example¶

// Run this code

#include <cstdint>
#include <filesystem>
#include <iostream>

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¶

space_info information about free and available space on the filesystem
(C++17) (class)