Show HN: ZSV – A fast, SIMD-based CSV parser and CLI toolkit

zsv was built because I needed a library to integrate with my application, and other CSV parsers had one or more of a variety of limitations (couldn't handle "real-world" CSV or malformed UTF8, were too slow, degraded when used on very large files, couldn't compile to web assembly, could not handle multi-row headers (seems like basically none of the other CSV parsers do this) etc-- more details are in the repo README). The closest solution to what I wanted was xsv, but was not designed as an API and I still needed a lot of flexibility that wasn't already built into it.

My first inclination was to use flex/bison but that approach yielded surprisingly slow performance; SIMD had just been shown to be useful in unprecedented performance gains for JSON parsing, so a friend and I took a page from that approach to create what afaik (though I could be wrong) is now the fastest CSV parser (and most customizable as well) that properly handles "real-world" CSV.

When I say "real-world CSV": if you've worked with CSV in the wild, you probably know what I mean, but feel free to check out the README for a more technical explanation.

With parser built, I found that some of the use cases I needed it for were generic, so I wrapped them up in a CLI. Most of the CLI commands are run-of-the-mill stuff: echo, select, count, sql, pretty, 2tsv, stack. Some of the commands are harder to find in other utilities: compare (cell-level comparison with customizable numerical tolerance-- useful when, for example, comparing CSV vs data from a deconstructed XLSX, where the latter may look the same but technically differ by I've been using zsv for years now in commercial software running bare metal and also in the browser (see e.g. https://liquidaty.github.io/zsv/), so I finally got around to tagging v1.0.1 as the first production-ready release.

I'd love for you to try it out and would welcome any feedback, bug reports, or questions.