Suppose the following directory: C:\export As a command line argument in one of my applications, I get an absolute path to a file. I want to check if this file exists at some nested level inside of C:\export. Suppose the file passed in is: C:\export\blah\myfile.txt I would like to be able to call some sort of function that returns 'true' if the file (myfile.txt) exists within the directory tree rooted at C:\export. Now suppose this next file: C:\work\anotherfile.txt The function in question would return 'false' here since anotherfile.txt does not exist inside of c:\export. Something like the following would work for me. is_file_within_directory_tree( "C:\export", "C:\work\anotherfile.txt" ); // returns false is_file_within_directory_tree( "C:\export", "C:\export\blah\myfile.txt" ); // returns true Is there an easy way to do this with Boost.Filesystem? Thanks, Michael Marcin