After mac update the system environment variables suddenly gone

This morning've updated \ (mac \) after the afternoon found a lot of environmental suddenly gone, looking for information after the discovery of the problem. . .
1. terminal from the original \ (the bash \) becomes \ (zsh \) , then the need to \ (~ / .zshrc \) rearmost added \ (~ Source / .bash \ _profile \) ;
2. By \ (xcode \) Download the environment did not, say online information after each update \ (xcode \) are unloaded (obviously there is \ (xcode \) software, do not understand = _ =), so we need to re Download \ (xcode: xcode-select --instal \)