Unanticipated Context Awareness for Software Configuration Access using the getenv API

Configuration files, command-line arguments and environment variables are the dominant tools for local configuration management today. When accessing such program execution environments, however, most applications do not take context, e.g. the system they run on, into account. The aim of this paper is to integrate unmodified applications into a coherent and context-aware system by instrumenting the getenv API. We propose a global database stored in configuration files that includes specifications for contextual interpretations and a novel matching algorithm. In a case study we analyze a complete Debian operating system where every getenv API call is intercepted. We evaluate usage patterns of 16 real-world applications and systems and report on limitations of unforeseen context changes. The results show that getenv is used extensively for variability. The tool has acceptable overhead and improves context-awareness of many applications.