Until now, to perform a task or set anything for a given shell, we had to execute the needed commands in a shell. One of the main limitations to this approach is that the same configuration won't be available in a new shell. In a lot of cases, a user may want that whenever he or she launches a new shell, whereas instead a new customized configuration on top of the default configuration is available for use. For customizing bash, three files are available in a user's home directory that get executed by default whenever a user launches a new bash. These files are bashrc, .bash_profile, and .bash_logout.