Fact extraction from bash in support of script migration

Abstract

Owl Computing Technologies provides software and hardware that facilitates secure unidirectional data transfer across the Internet. Bash scripts are used to facilitate customer installation of Owl's client/server software, and to provide high level management, control, and monitoring of client/server interfaces. With the evolution of more robust scripting languages, Owl now wishes to convert their bash scripts to other scripting languages. As part of this conversion exercise the configuration and customization of their bash scripts will no longer involve direct end user modifications of the script logic. It will instead be achieved through appropriate modification of a supporting XML configuration file, which is read by each script. This avoids the risk that end users erroneously change scripts, and makes legitimate end user customization of their scripts simpler, more obvious, and easier to discern. An open source fact extractor was implemented that determines the dynamic usage made of every variable within an arbitrary bash script. This tool reports errors in a script and generates an XML configuration file that describes variable usage. Those variables whose value may not be assigned by an end user are manually removed from this XML configuration file. A second program reads this configuration file, generates the appropriate bash variable assignment statements, and these are then applied within bash by using the bash eval command. Collectively this provides a simple mechanism for altering arbitrary bash scripts so that they use an external XML configuration file, as a first step in the larger exercise of migrating bash scripts to other scripting languages.