       source Same as ., except that  the  current  directory  is
              always  searched  and  is  always  searched  first,
              before directories in path.

       . file [ arg ... ]
              Read commands from file and  execute  them  in  the
              current  shell  environment.  If file does not con-
              tain a slash, or if PATH_DIRS  is  set,  the  shell
              looks  in the components of path to find the direc-
              tory containing file.  Files in the current  direc-
              tory  are  not read unless "." appears somewhere in
              path.  If any arguments arg are given, they  become
              the   positional  parameters;  the  old  positional
              parameters are restored when the file is done  exe-
              cuting.   The exit status is the exit status of the
              last command executed.
