Is there a tool that can print out a bash script with the variables substituted?

Say I have a bash script that takes some environment variables and parameters and substitutes those variables in a script. Is there a tool that can show how the script with the substituted variables will look like? Take this short script for instance. echo user = $USER host = $HOSTNAME The program would output echo user = vfclists host = unixse So the script would be along the lines of expandscript script.sh --param1=xxxx --param2=xxxx --param3=xxxx and in addition to the environment variables filling the values of the params where they are set to the programs variables.