How are various shells configured, and in which order?

shell_config.md

ash & dash

login	interactive	files
N	N
N	Y	$ENV
Y	N	/etc/profile, ~/.profile
Y	Y	/etc/profile, ~/.profile, $ENV

bash

login	interactive	files
N	N	$BASH_ENV
N	Y	~/.bashrc
Y	N	/etc/profile, ~/.bash_profile, ~/.bash_login, ~/.profile
Y	Y	/etc/profile, ~/.bash_profile, ~/.bash_login, ~/.profile

bash invoked as sh

login	interactive	files
N	N	$ENV
N	Y	~/.bashrc
Y	N	/etc/profile, ~/.profile
Y	Y	/etc/profile, ~/.profile

csh (illumos)

login	interactive	files
N	N	/etc/csh.cshrc, ~/.tcshrc OR ~/.cshrc
N	Y	/etc/csh.cshrc, ~/.tcshrc OR ~/.cshrc
Y	N	/etc/csh.cshrc, /etc/csh.login, ~/.tcshrc OR ~/.cshrc, ~/.history, ~/.login
Y	Y	/etc/csh.cshrc, /etc/csh.login, ~/.tcshrc OR ~/.cshrc, ~/.history, ~/.login

tcsh

login	interactive	files
N	N
N	Y	~/.cshrc
Y	N
Y	Y	/etc/.login, ~/.tcshrc OR ~/.cshrc, ~/.login

ksh

login	interactive	files
N	N
N	Y	/etc/ksh.kshrc, $ENV
Y	N	/etc/profile, ./.profile ~/.profile
Y	Y	/etc/profile, ./.profile ~/.profile, /etc/ksh.kshrc, $ENV

zsh

login	interactive	files
N	N	/etc/zshenv, $ZDOTDIR/.zshenv
N	Y	/etc/zshenv, $ZDOTDIR/.zshenv, /etc/zshrc, $ZDOTDIR/.zshrc
Y	N	/etc/zshenv, $ZDOTDIR/.zshenv, /etc/zprofile, $ZDOTDIR/.zprofile, /etc/zlogin, $ZDOTDIR/.zlogin
Y	Y	/etc/zshenv, $ZDOTDIR/.zshenv, /etc/zprofile, $ZDOTDIR/.zprofile, /etc/zshrc, $ZDOTDIR/.zshrc, /etc/zlogin, $ZDOTDIR/.zlogin