boost::filesystem get relative path

Question

What methods of the boost::filesystem library can help me to get a path relative to another path?

I have a path /home/user1/Downloads/Books

Answer 1

The code in the provided answers is quite long on each line. Assuming that you wrote namespace fs = boost::filesystem; then this code gets you most of the way and looks easier to read to me:

    auto relativeTo( const fs::path& from, const fs::path& to )
    {
       // Start at the root path and while they are the same then do nothing then when they first
       // diverge take the entire from path, swap it with '..' segments, and then append the remainder of the to path.
       auto fromIter = from.begin();
       auto toIter = to.begin();

       // Loop through both while they are the same to find nearest common directory
       while( fromIter != from.end() && toIter != to.end() && *toIter == *fromIter )
       {
          ++toIter;
          ++fromIter;
       }

       // Replace from path segments with '..' (from => nearest common directory)
       auto finalPath = fs::path{};
       while( fromIter != from.end() )
       {
          finalPath /= "..";
          ++fromIter;
       }

       // Append the remainder of the to path (nearest common directory => to)
       while( toIter != to.end() )
       {
          finalPath /= *toIter;
          ++toIter;
       }

       return finalPath;
    }