jlif - JSON Line Formatter

A command-line tool for quickly scanning multi-object JSON logs and data streams, handling both single-line and multi-line JSON objects mixed with non-JSON content.

Overview

jlif processes continuous text streams from standard input, intelligently detecting JSON objects that may span multiple lines (such as pretty-printed JSON in logs), and formats them for improved readability while preserving non-JSON content unchanged. This makes it ideal for scanning application logs, API responses, and data streams where JSON objects are mixed with other text content.

Installation

Pre-built binaries for macOS, Linux, and Windows are available in the GitHub Releases section.

Usage

Basic usage:

# Pretty-print JSON with colors
tail -f app.log | jlif

# HTTP response with headers and JSON
curl -si https://randomuser.me/api/ | jlif

# Compact output without colors
cat data.jsonl | jlif -c --no-color

# Filter for error messages
kubectl logs pod | jlif -f "error"

# Show only JSON, hide other log lines
docker logs container | jlif -j

Options

Filtering

Filter flags can be combined:

The filter pattern matches against the serialized JSON string, not individual fields. Filtering is case-insensitive by default; use -s for case-sensitive matching.

Multi-line JSON

jlif automatically detects and assembles multi-line JSON objects. When a line starts with { or [ but isn't valid JSON, jlif buffers lines until a complete object forms or the buffer limit is reached.

Use --max-lines to increase the buffer for deeply nested JSON.

Examples

Kubernetes logs:

kubectl logs -f my-pod | jlif -f "error" -j

Docker logs:

docker logs -f container 2>&1 | jlif -j

Pipe to jq:

cat logs.jsonl | jlif -c --no-color | jq '.message'

Building

cargo build --release

License

This project is licensed under the Mozilla Public License 2.0 - see the LICENSE file for details.