Installing the command-line executable

Assuming you have Rust/Cargo installed, run this command in a terminal:

cargo install jlif

It will make the jlif command available in your PATH if you've allowed the PATH to be modified when installing Rust. cargo uninstall jlif uninstalls.

Back to the crate overview.

Readme

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

Option	Description	Default
`--max-lines <N>`	Max lines to buffer for multi-line JSON	10
`-f, --filter <PATTERN>`	Regex filter pattern	—
`-s, --case-sensitive`	Case-sensitive filtering	Off
`-v, --invert-match`	Invert filter (show non-matching)	Off
`-j, --json-only`	Show only JSON content	Off
`-c, --compact`	Compact single-line output	Off
`--no-color`	Disable syntax highlighting	Off

Filtering

Filter flags can be combined:

Flags	Result
`-f "error"`	Show lines containing "error"
`-f "error" -j`	Show only JSON containing "error"
`-f "error" -v`	Show lines NOT containing "error"

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.