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std::filesystem::space

From cppreference.com
< cpp‎ | filesystem
 
 
Filesystem library
 
Defined in header <filesystem>
(1) (since C++17)
std::filesystem::space_info space( const std::filesystem::path & p,
                                   std::error_code & ec ) noexcept;
(2) (since C++17)

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:

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

[edit] Parameters

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

[edit] Return value

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

[edit] 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.

[edit] Notes

space_info.available may be less than space_info.free.

[edit] 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

[edit] See also

(C++17)
information about free and available space on the filesystem
(class) [edit]
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