Proper place to put shell prompt(PS1) when use sh/bash/zsh together

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http://unix.stackexchange.com – I'm using dash(sh) or bash or zsh. If possible, I would prefer to put in common place. I want to put proper PS1 settings when I interactive with shell, so these situation should be considered login (show PS1) su sudo script (Don't show PS1) I was put PS1 on .bashrc, but it seems not always workable. (HowTos)