appmasterio/jc-rs repository overview

⁠jc-rs

Convert the output of command-line tools, file formats and strings to JSON — as a single static binary in a scratch image. No shell, no libc, no package manager: the image is the binary and its licence, nothing else.

$ ps aux | docker run --rm -i appmasterio/jc-rs --ps | jq '.[0]'
$ docker run --rm -i appmasterio/jc-rs --df < df.txt
$ tail -f access.log | docker run --rm -i appmasterio/jc-rs -u --clf-s

⁠What it is

A Rust implementation of the schemas defined by jc⁠, the tool that decided which commands are worth parsing and what the JSON for each should look like. jc's one weakness is the Python runtime: ~160 ms of interpreter startup on every invocation, and a dependency you cannot put in a scratch container. This is that tool as a static binary.

Compatibility with jc is 100% — 934 of 934 oracle-valid fixture pairs from jc's own corpus, measured on every commit and published whatever it says. CI fails below 100%, so it cannot drift quietly. The rule that makes the number mean something: a fixture only counts when jc itself reproduces it exactly, and everything that does not qualify is reported by category rather than dropped.

⁠Speed

Median of 5–11 runs against jc 1.25.7 on Python 3.12, same harness both sides (ci/bench-vs-jc.sh⁠):

The gap is largest at startup, which is why it matters most in loops, git hooks and per-host automation rather than at an interactive prompt.

⁠Usage

Same interface as jc — 238 parsers, -p to pretty-print, -y for YAML, -r for raw output, -M for metadata.

$ docker run --rm appmasterio/jc-rs --help
$ docker run --rm appmasterio/jc-rs -l          # list parsers

Streaming parsers emit NDJSON as input arrives — one JSON object per line, not one array at the end. Add -u to flush per record, which is what a live pipe needs:

$ ping example.com | docker run --rm -i appmasterio/jc-rs -u --ping-s

Magic syntax (jc-rs df -h) needs the command inside the container, and this image deliberately has nothing else in it. Pipe instead, or use the standalone binary.

⁠Tags

• latest — the most recent release
• vX.Y.Z — a specific release

2.3 MB compressed, linux/amd64 only today.

⁠Elsewhere

cargo binstall jc-rs                    # prebuilt binary, no compile
cargo install jc-rs                     # from source
brew install OlegSotnikov/tap/jc-rs     # macOS and Linux
npm install jc-rs-wasm                  # WebAssembly, browser or Node

Static binaries for five targets, with shell completions and `SHA256SUMS attached to every release⁠.

Source, the full compatibility report and what is left to do https://github.com/OlegSotnikov/jc-rs⁠