Where to get 20newsgroups dataset that contains 20newsgroups.dat


Following https://meta-toolkit.org/search-tutorial.html, I tried to run ./index config.toml with a downloaded 20newgroups data set. But it failed with error:
1537626968: [info] Existing inverted index detected as invalid; recreating (/home/al/meta/src/index/inverted_index.cpp:104)
1537626968: [info] Creating index: 20news-inv (/home/al/meta/src/index/inverted_index.cpp:118)
terminate called after throwing an instance of ‘meta::io::mmap_file::mmap_file_exception’
what(): error obtaining file descriptor for …/data//20newsgroups/20newsgroups.dat

I checked the files under 20newsgroups, there is no dat file there.
How to solve this issue?