Not really a true FAQ yet, but this might still be of interest if you're playing (or trying to) with Koopa.
Q. Why won't the file I pick show up in the results ?
When picking a file to parse the GUI will filter out all files which don't end in .cbl or .cpy. This is because you can also pick a folder for parsing and then the GUI will traverse that folder and process all Cobol files it finds. One solution is to rename the files. Another is to pass the allowed extensions as an extra parameter on the command line:
java -cp koopa.jar -Dkoopa.cobolFileExtensions=cob,txt,foo
Q. How do I export the syntax tree to XML ?
Solution 1. Open the Cobol file in the GUI. Then go to the "Syntax tree" menu, and choose "Export to XML".
Solution 2. From the command line, invoke:
java -cp koopa.jar koopa.app.cli.ToXml [--free-format] <cobol-file> <xml-file>
This assumes your're using the executable jar which you can download from Sourceforge.