setting options in bash

> man bash
>      When bash is invoked as an interactive login shell, or as  a
>      non-interactive  shell  with  the  --login  option, it first
>      reads and executes commands from the file  /etc/profile,  if
>      that  file  exists.   After  reading that file, it looks for
>      ~/.bash_profile,  ~/.bash_login,  and  ~/.profile,  in  that
>      order,  and  reads  and executes commands from the first one
>      that exists and is readable.  The --noprofile option may  be
>      used when the shell is started to inhibit this behavior.

>      When a login shell exits, bash reads and  executes  commands
>      from the file ~/.bash_logout, if it exists.

>      When an interactive shell that  is  not  a  login  shell  is
>      started, bash reads and executes commands from ~/.bashrc, if
>      that file exists.  This may be inhibited by using the --norc
>      option.   The  --rcfile  file option will force bash to read
>      and execute commands from file instead of ~/.bashrc.