Environment variable for Apple Shake 4.1 Where is Shake's environment variable located in macOS allowing to launch Shake.app via Terminal session in High Sierra? 

There's no Shake's variables in ~/.bash_profile, /etc/profile and /etc/bashrc.
Bash command which shake gives me the following result:

/usr/bin/shake


And the content of the shake file in /usr/bin/ contains a script like this:

# set env var, NR_SHAKE_LOCATION if not set

if ${?NR_SHAKE_LOCATION} == 0 then
    pushd `dirname $0` &gt;&amp; /dev/null
    setenv NR_SHAKE_LOCATION /Applications/Shake
    popd &gt;&amp; /dev/null
endif

# launch shake

exec ${NR_SHAKE_LOCATION}/shake.app/Contents/MacOS/shake $argv:q