make_relative_filename - Tries to make a relative filename from absolute path and filename. Allegro game

       Attempts to make a relative filename from an absolute path and an  absolute  filename,  storing  at  most
       `size'  bytes  into  the `dest' buffer. This function won't work if the paths are not canonical under the
       current platform (see canonicalize_filename()). Also, `dest' cannot be used as input value for `path'  or
       `filename'. Example:

          char base[] = "/long/absolute/path/program.exe";
          char user_input[] = "/nice/and/short.txt";
          ...
          make_relative_filename(buf, base, user_input, sizeof(buf));
          /* Under Unix buf would contain:
             ../../../nice/and/short.txt */

       make_relative_filename  - Tries to make a relative filename from absolute path and filename. Allegro game
       programming library.

       Returns a copy of the `dest' parameter if it succeeds or NULL if it fails (eg. under DOS, one path starts
       with "C:\" and another with "A:\").

make_absolute_filename(3alleg4), is_relative_filename(3alleg4), canonicalize_filename(3alleg4)

Allegro                                           version 4.4.3                  make_relative_filename(3alleg4)

#include<allegro.h>char*make_relative_filename(char*dest,constchar*path,constchar*filename,intsize);