Create new file from templates with bash script

You can do this using a heredoc. e.g.

generate.sh:

#!/bin/sh

#define parameters which are passed in.
PORT=$1
DOMAIN=$2

#define the template.
cat  << EOF
This is my template.
Port is $PORT
Domain is $DOMAIN
EOF

Output:

$ generate.sh 8080 domain.example

This is my template.
Port is 8080
Domain is domain.example

or save it to a file:

$ generate.sh 8080 domain.example > result