In JRE-9/lib directory (at least on Windows), there is a new file called modules whose size is about 107 MB. Is it possible to extract that file or maybe list java modules within it?
I can see that a new tool called jmod is available at jdk-9/bin/jmod.exe, but that is for reading .jmod files which is located at jdk-9/jmods and it cannot read the file modules.
The modules file is a container file. It's internal to the JDK and the format is not documented (it may change at any time). For troubleshooting purposes, the jimage tool in the bin directory can be used to list or extract the contents.