CLI Log Cleaner 🧹

A lightweight TypeScript-based CLI tool to clean noisy log files and keep only meaningful entries. Simple usage, multiple log formats, and sane defaults for real-world debugging.

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✨ Features

• 🔍 Log level filtering (INFO, WARN, ERROR, FATAL, etc.)
• 🧠 Severity-based matching
  ERROR shows ERROR + FATAL, WARN shows WARN + ERROR + FATAL
• 📄 Multiple log formats supported (auto-detected)
  • Simple logs (2026-01-12 ERROR something broke)
  • Pipe/enterprise logs (| Info | Service | ...)
• 🔄 Context lines before/after matching logs
• 🪄 Auto-detect log format (no flags needed)
• 🖥️ Works on Windows / macOS / Linux

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📦 Installation

Prerequisites

• Node.js v18+
• npm

Install dependencies

npm install

Run locally (dev mode)

npm run dev -- your.log -- --level ERROR --context 1

⚠️ Note for Windows users: when using npm run, you must add a second -- before CLI flags.

Build

npm run build

Link as global CLI

npm link

Then you can run:

log-clean your.log --level ERROR

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🚀 Usage

Basic usage

log-clean <file> [options]

Options

Option	Description	Default
-l, --level <level>	Minimum log level	ERROR
-c, --context <n>	Lines before/after the matched log	0
-o, --output <file>	Output file name	cleaned.log

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🧪 Examples

1️⃣ Only ERROR and above

log-clean app.log --level ERROR

Output includes:

ERROR
FATAL

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2️⃣ WARN and above with context

log-clean app.log --level WARN --context 1

Shows WARN, ERROR, FATAL logs plus surrounding lines that also match severity rules.

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🧠 Supported Log Formats

The tool supports multiple log formats implicitly, without requiring explicit configuration. As long as a log line contains a recognizable log level, it can be filtered.

Below are the officially supported formats with example log lines for each log level.

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1️⃣ Simple Timestamp + Level Logs

Common in many backend services and scripts.

2026-01-12 DEBUG Token refreshed
2026-01-12 INFO App started
2026-01-12 WARN Slow response
2026-01-12 ERROR Payment failed
2026-01-12 FATAL System crashed

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2️⃣ Pipe / Enterprise Logs

Often seen in enterprise or agent-based systems.

2026-01-13 21:58:26.4614 | DEBUG | TEST | Debug message
2026-01-13 21:58:26.4614 | INFO  | TEST | Information message
2026-01-13 21:58:26.4614 | WARN  | TEST | Warning message
2026-01-13 21:58:26.4614 | ERROR | TEST | Error message
2026-01-13 21:58:26.4614 | FATAL | TEST | Fatal error message

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3️⃣ Bracketed Structured Logs (Go / log4go-style)

Common in Go applications with structured logging and caller information.

[2023/10/12 22:06:47 +03] [DEBUG] (pkg/logger.Debug:12) Debugging startup sequence
[2023/10/12 22:06:47 +03] [INFO]  (pkg/logger.Info:34) Application started
[2023/10/12 22:06:47 +03] [WARN]  (pkg/logger.Warn:56) Configuration file missing, using defaults
[2023/10/12 22:06:52 +03] [ERROR] (pkg/logger.Error:78) Failed to connect to database
[2023/10/12 22:06:52 +03] [FATAL] (pkg/logger.Fatal:91) Unrecoverable error, shutting down

Nested logs inside pipe sections are also supported:

[2023/10/12 22:06:52 +03] [ERROR] (pkg/logger.Error:78) ENGINE | [10/12/23 22:06:52] [ERROR] inner component failure

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4️⃣ Java / Log4j / Logback Logs

Widely used in Java and JVM-based applications.

2026-01-12 21:58:26,461 DEBUG [main] com.app.Service - Debug message
2026-01-12 21:58:26,461 INFO  [main] com.app.Service - Application started
2026-01-12 21:58:26,461 WARN  [main] com.app.Service - Deprecated API usage
2026-01-12 21:58:26,461 ERROR [main] com.app.Service - Payment failed
2026-01-12 21:58:26,461 FATAL [main] com.app.Service - JVM crash detected

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5️⃣ Python Logging

Default or customized Python logging module output.

2026-01-12 21:58:26,461 - DEBUG - worker - Debug message
2026-01-12 21:58:26,461 - INFO  - worker - Task started
2026-01-12 21:58:26,461 - WARN  - worker - Retry attempt
2026-01-12 21:58:26,461 - ERROR - worker - Task failed
2026-01-12 21:58:26,461 - FATAL - worker - Worker crashed

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6️⃣ Syslog (Linux / Infrastructure)

Common in Linux servers and infrastructure logs.

Jan 12 21:58:26 server1 DEBUG sshd[1234]: Debugging SSH key exchange
Jan 12 21:58:27 server1 INFO  sshd[1234]: Accepted password for user from 192.168.1.10
Jan 12 21:58:28 server1 WARN  sshd[1234]: Authentication attempt failed for invalid user
Jan 12 21:58:29 server1 ERROR sshd[1234]: Failed to read authorized_keys file
Jan 12 21:58:30 server1 FATAL sshd[1234]: Critical failure, sshd shutting down

• Cleaner logic is independent of log format
• Parsers are extensible and isolated

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🧑‍💻 Development

npm run dev
npm run build

Project structure:

src/
├─ index.ts        # CLI entry point
├─ cleaner.ts      # Core filtering logic
├─ logEntry.ts     # Shared log model
├─ types.ts        # Log levels & enums
└─ parsers/
   ├─ AutoParser.ts
   ├─ SimpleParser.ts
   ├─ PipeParser.ts
   └─ LogParser.ts

Happy log cleaning 🧘‍♀️