How get file path from std::ifstream in c++

Question

You can't, std::ifstream does not store this information.

What you can do, however, is:

1. use process' current working directory to compose the absolute path yourself, or

2. use a library like Boost.Filesystem library to transform between relative and absolute paths.

   boost::filesystem::path abs_path = boost::filesystem::complete("./rel/path");
   std::string abs_path_str = abs_path.string();
   

The fstream classes have no functionality for accessing or processing the name used to open the file with, and the C++ Standard Library has no filename processing functions - you will have to write the code yourself, or use a third-party library or operating system-supplied functions.

I don't think it is possible for a std::fstream. I did it for a FILE * on Windows (in a non-portable way). See from file object to file name.

Have you considered extending the ifstream with your own class that remembers the file name?