Setting up an enriched, system-wide prompt again raised the question where to put the definition code. Spreading the snippet all over the home-located profile-(.bash_profile) and resource(.bashrc)-files is a bad idea, tedious to maintain, you know, don’t ever think about it.
Changing the global profile- and resource-files (/etc/profile , /etc/bashrc) won’t be of any much more brain either, since yet another system update may cause conflicts with the maintainers version. Just reading along the web, I found that there is some mechanism integrated with /etc/profile to source homebrewed definitions from a file within /etc/profile.d . Great, this is what I want, but, as far as I remember correctly, a profile will only be sourced once, upon login, in a login shell, right?!
Oohhm, still can’t recite that poem on command. On login, we source the environment (profile). We won’t do that for sub-shells because the environment will be derived. However, since a login shell is also an interactive shell usually, we still addionally source the aliase- und function-resources as well… And so on and forth in bare theory, which has been depicted nicely in man bash, in the invocation section in particular. Read this now for reference!
On the other hand, living system may not stay with the initial ideas very long, in practice a question may have a multiple of answers (or the other way round). So I parsed and instrumented the profile- and resource-loading process to see what really happens under the bonnt. See what I’ve found.
As being spotted on 
Bitbach's Blog 