function get_version_from_filename, filename

   version_start_pos = strpos(filename, '_v', /reverse_search) + 2
   
   ; possible version formats are '003' or '03.10'...
   ; in the first case, there are 3 characters, followed by either a '-' or '.'
   ; in the second case, there are 5 characters, followed by either a '-' or '.'
   ; so, if the third character is '.' then take 5 chars total from version_start_pos
   ; otherwise, take 3 chars total from version_start_pos 
   version_check_char = strmid(filename, version_start_pos+2, 1)
   
   if version_check_char eq '.' then version = strmid(filename, version_start_pos, 5) $
   else version = strmid(filename, version_start_pos, 3)
   
   print, get_routine_name() + '  file version: ', version
   
   return, version
   
end