If a software package has optional compile-time features, the user can give configure command line options to specify whether to compile them. They should only cause parts of the program to be built rather than left out. Whether each feature is included or not by default, and which arguments are valid, is up to you. The name feature indicates an optional user-level facility. It should consist only of alphanumeric characters and dashes.
Some software packages require complex site-specific information.
Some examples are host names to use for certain services, company names, and email addresses to contact. Since some configuration scripts generated by Metaconfig ask for such information interactively, people sometimes wonder how to get that information in Autoconf-generated configuration scripts, which aren't interactive. Such site configuration information should be put in a file that is edited only by users , not by programs. The location of the file can either be based on the prefix variable, or be a standard location such as the user's home directory. It could even be specified by an environment variable.