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std::filesystem::space(3)     C++ Standard Libary    std::filesystem::space(3)

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 path-
       name 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::uint-
       max_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 er-
       rors, 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::filesys-
       tem::space(dir, ec);
		for  (auto  x  : {si.capacity, si.free,	si.available, disk_us-
       age_percent(si)})
		    std::cout	<<   "	 "   <<	  std::setw(width)   <<	  sta-
       tic_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)

http://cppreference.com		  2024.06.10	     std::filesystem::space(3)

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