filesystem

`std::filesystem::absolute(path)`

This function attempts to convert the provided path into an absolute path.
If the path is relative, it resolves it relative to the current working directory.
If the path is already absolute, it simply returns the same path.

std::unique_ptr<FILE, decltype(&_pclose)> pipe(_popen(cmd, "r"), _pclose);

std::unique_ptr<FILE, decltype(&_pclose)>:
- This declares a std::unique_ptr that manages a FILE* resource.
- The second template parameter, decltype(&_pclose), specifies the type of the custom deleter function, which is _pclose in this case.
- _pclose is used to close the pipe created by _popen.
_popen(cmd, "r"):
- _popen is a Microsoft-specific function (used on Windows) that opens a process by creating a pipe, for example, to execute a shell command.
- The cmd is the command to execute.
- The "r" mode specifies that the pipe is opened for reading (standard output of the command).
_pclose:
- _pclose is a corresponding function to close the pipe opened by _popen.
std::unique_ptr Construction:
- The std::unique_ptr is initialized with:
- The FILE* pointer returned by _popen.
- The _pclose function, which acts as the custom deleter.