Practical recipes for everyday development

These recipes solve small, common developer tasks with commands you can copy and adapt. They assume lingua --version works and that every file or program you execute is trusted.

Pick a recipe by outcome

You need to…	Recipe
inspect an API response	Format JSON from curl
inspect a token without uploading it	Read a JWT header and payload
create a URL query safely	Encode one URL component
normalize generated files	Guard JSON in a Git hook
run a repository check	Expose Lingua through package.json
add a CI gate	Pin the CLI in GitHub Actions
reproduce a captured run	Require an exact Capsule replay
use Lingua from Windows	Keep the exit code in PowerShell

Work with API and web data

Format JSON from curl

Keep the transformed JSON on stdout so it can continue into jq:

curl -fsSL https://api.github.com/repos/johnny4young/lingua \
  | lingua utility json-format --quiet \
  | jq '{name, stargazers_count, open_issues_count}'

curl -f makes HTTP errors fail the pipeline. In Bash CI jobs, add set -o pipefail so an earlier failure cannot be hidden by a later command.

Minify a JSON release artifact

lingua utility json-minify --input config/runtime.json --quiet \
  > dist/runtime.min.json

The command parses before writing, so malformed JSON fails instead of producing a partially transformed artifact.

Read a JWT header and payload

printf '%s' "$ACCESS_TOKEN" \
  | lingua utility jwt-decode --quiet \
  | jq '{algorithm: .header.alg, subject: .payload.sub, expires: .payload.exp}'

This decodes local text only. It does not verify the signature, issuer, audience, expiry, or authorization. Never treat decoded claims as trusted identity.

Encode one URL component

query=$(printf '%s' 'state:open label:"good first issue"' \
  | lingua utility url-encode --quiet)

curl -fsSL "https://api.github.com/search/issues?q=${query}" | jq '.total_count'

url-encode is for a component such as one query value, not for re-encoding an entire URL.

Break an absolute URL into fields

printf '%s' 'https://example.com:8443/api/items?limit=20#results' \
  | lingua utility url-parse --quiet \
  | jq '{origin, pathname, searchParams}'

url-parse rejects relative URLs deliberately. Resolve a relative path against its base before passing it to the utility.

Encode or decode text as Base64

encoded=$(printf '%s' 'local developer value' | lingua utility base64-encode --quiet)
printf '%s' "$encoded" | lingua utility base64-decode --quiet

The CLI contract is UTF-8 text. Base64 is an encoding, not encryption, and this recipe is not intended for arbitrary binary files or secrets.

Escape a snippet for safe HTML text

printf '%s' '<button data-id="42">Run & inspect</button>' \
  | lingua utility html-entity-encode --quiet

This escapes text content. It does not sanitize an HTML document or make untrusted markup safe to execute.

Normalize text and developer data

Compute a text digest

digest=$(lingua utility hash \
  --input release-notes.md \
  --option algorithm=SHA-256 \
  --quiet)
printf 'release-notes.md  %s\n' "$digest"

The digest covers the UTF-8 text read by the CLI. Use an operating-system checksum tool when byte-for-byte hashing of arbitrary binary files is required.

Sort and deduplicate changed paths

git diff --name-only origin/main...HEAD \
  | lingua utility line-sort \
      --option unique=true \
      --option caseInsensitive=true \
      --quiet

Add --option numeric=true when values such as fixture2 and fixture10 should use natural ordering.

Produce a stable identifier style

printf '%s' 'HTTP response cache key' \
  | lingua utility string-case --option target=snake --quiet

printf '%s' 'Guía rápida para equipos' \
  | lingua utility slugify --option separator=hyphen --quiet

Use string-case for code-oriented naming (camel, snake, kebab, and others). Use slugify for an ASCII URL or filename segment.

Replace a repeated source pattern

lingua utility regex-replace \
  --input src/legacy.ts \
  --option pattern='console\\.log' \
  --option flags=g \
  --option replacement=logger.info \
  --quiet > /tmp/legacy.updated.ts

diff -u src/legacy.ts /tmp/legacy.updated.ts

Preview the diff before replacing the original file. Quote the pattern so the shell does not interpret backslashes or metacharacters.

Inspect suspicious Unicode

git log -1 --pretty=%B | lingua utility string-inspect --quiet

The result distinguishes graphemes, code points, UTF-16 units, UTF-8 bytes, zero-width characters, and bidirectional controls—useful when two strings look identical but compare differently.

Convert a timestamp during incident review

printf '%s' '1735689600' | lingua utility timestamp --quiet

The result includes ISO 8601, epoch milliseconds, and epoch seconds. Record the original timezone separately when it matters; a Unix epoch represents an instant, not the author’s timezone.

Convert an integer without losing precision

printf '%s' '9007199254740993' \
  | lingua utility number-base \
      --option from=10 \
      --option to=16 \
      --option prefixOutput=true \
      --quiet

The converter uses integer arithmetic rather than floating-point conversion, so values above JavaScript’s safe-integer limit remain exact.

Generate test identifiers

printf 'generator-input-is-ignored' \
  | lingua utility uuid \
      --option format=v7 \
      --option count=5 \
      --quiet

uuid is a generator: it still receives stdin because every utility has one text-input contract, but it intentionally ignores that input. Generated values are not deterministic snapshots.

Translate a schedule into cron

printf '%s' 'weekdays at 9:30' \
  | lingua utility cron-phrase --option annotate=true --quiet

Keep annotate=true while reviewing the expression: the extra comment lines surface assumptions and cron caveats. Test the final schedule in the timezone and cron implementation that will run it.

Inspect a design token color

printf '%s' 'rgba(14, 165, 233, 0.75)' \
  | lingua utility color-convert --quiet

The output presents equivalent HEX, RGB/RGBA, and HSL forms for quick comparison.

Run repository tools consistently

Pass a fixture as stdin

lingua run ./scripts/normalize.py \
  --stdin ./fixtures/raw-event.json \
  --timeout 45000

Use --stdin when the input already has a path. It avoids a fragile shell pipeline and makes the fixture visible in the invocation.

Forward arguments to the program

lingua run ./scripts/check.ts \
  --timeout 60000 \
  -- --changed-only --format=json

Everything after -- belongs to check.ts. Lingua does not parse or reorder those tokens.

Run a conventional project root

lingua run ./tools/release-audit --timeout 120000

Directory detection supports conventional package.json, go.mod, Cargo.toml, and common single-file entry points. Run the framework command directly when a repository needs custom orchestration or a permanent server.

Expose Lingua through package.json

Pin the CLI in devDependencies, then give collaborators one memorable script:

{
  "devDependencies": {
    "@linguacode/cli": "1.3.0"
  },
  "scripts": {
    "check:local": "lingua run ./scripts/check.ts --timeout 60000 -- --changed-only",
    "check:capsules": "lingua capsule validate ./artifacts/latest.capsule.json --quiet"
  }
}

npm run check:local

Commit the lockfile. Upgrade the pinned version only after the same checks pass in your repository.

Add a Make target

.PHONY: verify-fixtures
verify-fixtures:
	lingua run ./scripts/verify-fixtures.py --stdin ./fixtures/events.ndjson --timeout 90000

The recipe line must begin with a tab. Make preserves Lingua’s exit code, so a failed run fails the target.

Guard JSON in a Git hook

Use a temporary file instead of rewriting a staged file automatically:

#!/usr/bin/env bash
set -euo pipefail

tmp=$(mktemp)
trap 'rm -f "$tmp"' EXIT

lingua utility json-format --input config/app.json --option indent=2 --quiet > "$tmp"
if ! cmp -s config/app.json "$tmp"; then
  echo 'config/app.json is not in canonical format' >&2
  diff -u config/app.json "$tmp" || true
  exit 1
fi

Install it with your repository’s existing hook manager. Hooks can be bypassed, so keep the same invariant in CI.

Put Lingua in automation

Pin the CLI in GitHub Actions

name: CLI checks
on: [pull_request]

jobs:
  verify:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with:
          node-version: 24
          cache: npm
      - run: npm ci
      - run: npx --no-install lingua run ./scripts/check.ts --json
      - run: npx --no-install lingua capsule validate ./artifacts/example.capsule.json --quiet

This assumes @linguacode/cli is pinned in the repository and lockfile, as in the package.json recipe. Install each language toolchain explicitly when the target is not JavaScript or TypeScript.

Preserve structured output and the exit code

#!/usr/bin/env bash
set -uo pipefail

result=$(lingua run ./scripts/healthcheck.ts --json)
status=$?

printf '%s\n' "$result" | jq .
if (( status != 0 )); then
  printf 'Lingua failed with exit code %d\n' "$status" >&2
fi
exit "$status"

Do not append || true to a gate unless failure is intentionally advisory. The JSON body explains the failure; the exit code decides whether automation continues.

Offer missing-runtime recovery without parsing prose

result=$(lingua run ./worker.py --json)
status=$?

if (( status == 3 )); then
  printf '%s\n' "$result" | jq '{reason, recovery}' >&2
fi
exit "$status"

Exit code 3 means a capability is unavailable. The structured recovery object can contain the runtime, executable, install command or guide, and verification command.

Validate every Capsule artifact

#!/usr/bin/env bash
set -euo pipefail

while IFS= read -r -d '' capsule; do
  lingua capsule validate "$capsule" --quiet
done < <(find artifacts -name '*.capsule.json' -type f -print0)

This validates shape and limits without executing stored source. Use -print0 so filenames containing spaces remain one item; set -e stops on the first invalid artifact.

Require an exact Capsule replay

lingua capsule replay ./artifacts/release-check.capsule.json \
  --timeout 60000 \
  --json \
  | jq -e '.ok == true and .comparison.matches == true'

Replay itself can exit 0 when the program ran successfully but differed from the recorded result. jq -e turns exact comparison into an explicit CI policy. Replay only trusted Capsules.

Build a small container image

FROM node:24-bookworm-slim

RUN npm install --global @linguacode/cli@1.3.0
WORKDIR /workspace
ENTRYPOINT ["lingua"]
CMD ["--help"]

docker build -t local/lingua-cli .
docker run --rm -i local/lingua-cli utility json-format --quiet \
  < fixtures/payload.json

Mount trusted source plus the required language toolchain when using lingua run. The container is the isolation boundary; Lingua is not an OS sandbox by itself.

Use native shell patterns

Bootstrap completion on a workstation

lingua completion --dry-run
lingua completion

The first command shows every detected shell and target file. The second asks once before writing. Homebrew installations place Bash, Zsh, and Fish completion files automatically.

Keep the exit code in PowerShell

$result = lingua run .\scripts\check.ts --json | ConvertFrom-Json
$status = $LASTEXITCODE

$result | ConvertTo-Json -Depth 8
if ($status -ne 0) {
  Write-Error "Lingua failed with exit code $status"
}
exit $status

Capture $LASTEXITCODE immediately after lingua; another native command can replace it.

Format a file in PowerShell

Get-Content .\config\app.json -Raw |
  lingua utility json-format --option indent=4 --quiet |
  Set-Content .\config\app.formatted.json -Encoding utf8

if ($LASTEXITCODE -ne 0) { exit $LASTEXITCODE }

Write to a second file first. Review or compare it before replacing the original.

Discover what your installed version supports

The installed registry is the source of truth when scripts must work across CLI versions:

lingua list utilities --json \
  | jq -r '.utilities[] | [.id, (.optionKeys | join(","))] | @tsv'

lingua --help
lingua utility --help
lingua run --help

Prefer discovery over guessing an adapter option. For stable automation, pin the CLI version and commit your package lockfile or immutable installer metadata.