tianonfmt

An opinionated formatter for jq, shell scripts, Dockerfiles (including Dockerfile.template files), and Markdown -- enforcing my personal style conventions across my Docker Official Images work, personal tools, and infrastructure scripts.

Supported types

File type is detected from the path extension or name:

Extension / filename	Format
.jq	jq
Dockerfile, Dockerfile.*	Dockerfile
Dockerfile.template (with {{ }})	jq-template
.sh or bash/sh shebang	shell
.md	Markdown

For stdin (or files with unknown extensions), detection falls back to content heuristics: shebang → shell, FROM → Dockerfile, {{ → jq-template, everything else → jq.

Usage

With no file arguments, reads from stdin and writes to stdout:

$ tianonfmt < script.sh
$ tianonfmt < filter.jq

With file arguments and no flags, prints formatted output to stdout without modifying the files:

$ tianonfmt Dockerfile script.sh filter.jq

-w writes formatted output back to source files and prints the names of files that changed:

$ tianonfmt -w Dockerfile script.sh *.jq

-d prints a unified diff for each file that would change and exits non-zero if any diffs are found:

$ tianonfmt -d script.sh

-t (--tidy) applies idiomatic rewrites beyond basic formatting and fails (exit 1) if any constructs remain that I consider Wrong. Combine with -d to see exactly what needs changing:

• shell: #!/bin/bash → #!/usr/bin/env bash; || true → || :; which → command -v; set -e → set -Eeuo pipefail (bash) or set -eu (sh)
• Dockerfile RUN: &&-chained commands → set -eux; semicolon; separated form
• Dockerfile CMD/ENTRYPOINT: shell-form → exec form (with /bin/sh -c wrapper for commands using shell features)

$ tianonfmt -t -w script.sh Dockerfile
$ tianonfmt -t -d script.sh

Why?

Formatters are great -- gofmt is the obvious example -- but they only exist where someone bothered to write one, and they only enforce the conventions of whoever wrote them. I have strong opinions about how my code should look, and I got tired of those opinions living only in my head (or surfacing only in code review comments).

tianonfmt makes "run the formatter" the answer to style questions.

Style documentation lives in docs/. None of it is exhaustive, and some of it is probably wrong -- but it's interesting.

Attribution

The research, corpus analysis, style documentation, and initial implementation were produced by "claude my eyes right out". Tianon was harmed in the creation of this tool.