Simple and standard way to generate files based on templates?

For my projects I need a way to generate some files based on template ones. I envision it this way: * a template file contains data with something like {{var1}} in place of the variables to be replaced * other file contains a list of key = value values * after applying a tool, a new file with concrete values should be generated Instead of the 2nd file, a list of key = value pairs could be provided via the command line or, which is the same thing, some keys may require environmental variables instead of the keys-value in the 2nd file. Are there **standard and well known utilities** used in Linux/Unix world that can do that?