In Unix, almost all the popular shells provide options to customize the environment by using environment variables. To make these customizations permanent we can write these to special files that are specific to a user in a shell.
Once we write our customizations to these files, we keep on getting same customization when we open a new shell with same user account.
The special files for storing customization information for different shells at login time are:
- C shell: /etc/.login or ~/.cshrc
- TC shell: /etc/.login or ~/.tshrc
- Korn shell: ~etc/ksh.kshrc
- Bash: ~/.bash_profile