Envsubst

Use bash to replace variables in host

https://serverfault.com/questions/287688/templating-with-linux-in-a-shell-script

Example template file apache.tmpl:

<VirtualHost *:${PORT}>
    ServerName ${SERVER_NAME}
    ServerAlias ${SERVER_ALIAS}
    DocumentRoot "${DOCUMENT_ROOT}"
</VirtualHost>
Run envsubst and output result to new file my_apache_site.conf:

export PORT="443"
export SERVER_NAME="example.com"
export SERVER_ALIAS="www.example.com"
export DOCUMENT_ROOT="/var/www/html/"
envsubst < apache.tmpl > my_apache_site.conf
Output:

<VirtualHost *:443>
    ServerName example.com
    ServerAlias www.example.com
    DocumentRoot "/var/www/html/"
</VirtualHost>