From time to time you may want to reset your environment; either because you have changed your .profile or .login files, or because you've erased a variable.
To reset the environment, re-execute your login file. Under the Bourne or Korn shells, type the following:
$Under the Korn shell (but not the Bourne shell) you can also type the following:
$(The dot is a command to execute the following file.)
Under the C shell, type the following: