AUSTIN: A tool for search based software testing for the C language and its evaluation on deployed automotive systems. Despite the large number of publications on Search--Based Software Testing (SBST), there remain few publicly available tools. This paper introduces AUSTIN, a publicly available SBST tool for the C language. The paper validates the tool with an empirical study of its effectiveness and efficiency in achieving branch coverage compared to random testing and the Evolutionary Testing Framework (ETF), which is used in-house by Daimler and others for Evolutionary Testing. The programs used in the study consist of eight non--trivial, real-world C functions drawn from three embedded automotive software modules. For the majority of the functions, AUSTIN is at least as effective (in terms of achieved branch coverage) as the ETF, and is considerably more efficient.