std::filesystem::space

Defined in header `<filesystem>`
std::filesystem::space_info space( const std::filesystem::path& p ); std::filesystem::space_info space( const std::filesystem::path& p, std::error_code& ec ) noexcept;		(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

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

The overload that does not take a std::error_code& parameter throws 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. The overload taking a std::error_code& parameter sets it to the OS API error code if an OS API call fails, and executes ec.clear() if no errors occur. Any overload not marked noexcept may throw std::bad_alloc if memory allocation fails.

Notes

space_info.available may be less than space_info.free.

Example

Run this code

#include <iostream>
#include <filesystem>
#include <cstdint>
 
void print_space_info(auto const& dirs, int width = 15)
{
    (std::cout << std::left).imbue(std::locale("en_US.UTF-8"));
    for (const auto s : {"Capacity", "Free", "Available", "Dir"})
        std::cout << "│ " << std::setw(width) << s << ' ';
    std::cout << '\n';
    std::error_code ec;
    for (auto const& dir : dirs) {
        const std::filesystem::space_info si = std::filesystem::space(dir, ec);
        std::cout
            << "│ " << std::setw(width) << static_cast<std::intmax_t>(si.capacity) << ' '
            << "│ " << std::setw(width) << static_cast<std::intmax_t>(si.free) << ' '
            << "│ " << std::setw(width) << static_cast<std::intmax_t>(si.available) << ' '
            << "│ " << dir << '\n';
    }
}
 
int main()
{
    const auto dirs = { "/dev/null", "/tmp", "/home", "/null" };
    print_space_info(dirs);
}

Possible output:

│ Capacity        │ Free            │ Available       │ Dir            
│ 84,417,331,200  │ 24,069,705,728  │ 21,492,748,288  │ /dev/null
│ 84,417,331,200  │ 24,069,705,728  │ 21,492,748,288  │ /tmp
│ 250,321,567,744 │ 37,623,181,312  │ 25,152,159,744  │ /home
│ -1              │ -1              │ -1              │ /null

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