$HOME/.profile

The system runs $HOME/.profile whenever you log in, after it runs /etc/profile. If you change your .profile, the changes don't go into effect until you next log in.

You should use your .profile to do the customizations that you need to do only once, or that you want all shells to inherit. For example, you could:

set environment variables; see “Environment variables”
run any commands that you need
set your file-permission mask; see “File ownership and permissions” in Working with Files

Note: If you want to create an alias, you should do it in your shell's profile (see “ksh's startup file”), not in .profile, because the shell doesn't export aliases. If you do set an alias in .profile, the alias is set only in shells that you start as login shells, using the -l option.

For an example of .profile, see the Examples appendix.