Miller

BSD-2-Clause named-field CSV/TSV/JSON munging (mlr)

DevOps / Tooling · OSS/MIT · 10k

Reviewed 2026-09-11 · last push 2026-10-15 · repo checked 2026-10-19

What's Good

BSD-2-Clause. johnkerl/miller (`mlr`). Format-aware pipelines over CSV, TSV, JSON, JSON Lines, and more — put, filter, join, stats, reshape with named fields. Docs at miller.readthedocs.io; source github.com/johnkerl/miller.

The Catch

Vs jq (JSON filter) and DuckDB (SQL over files): Miller is the *named-field CLI verb chain*, not a full SQL engine and not jq’s JSON DSL. Great for tabular streams; heavy analytics and joins may outgrow mlr into DuckDB/Polars. Distinct from yq’s document-shaped transforms.

Verdict

BSD-2-Clause tabular CLI. Free forever; munge CSV/TSV/JSON by field name before you open a notebook.

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