I am sitting with a bash script that does this
DOLLAR=$ envsubst < "in.conf" > "out.conf"
where I see these DOLLAR's in the in.conf file
proxy_set_header Host ${DOLLAR}host;
in out.conf have it become
proxy_set_header Host $host;
Question
envsubst does search and replace of environment variables, but what is the purpose of DOLLAR=$?