Pretty Logs

Pretty Logs is a powerful command-line tool designed to format and beautify JSON log output. It takes JSON-formatted log files as input and transforms them into human-readable output with customizable formatting options. This tool is particularly useful for developers and system administrators who need to analyze log files from applications that output JSON logs.

Features

Pretty Logs offers extensive customization options to handle various JSON log formats:

• Flexible timestamp formatting with customizable patterns
• Support for custom field mapping through command-line flags
• Error object detection and formatting
• Request/response object handling
• Template-based output formatting
• Support for large log files through efficient buffered reading
• Cross-platform compatibility (Linux, macOS, Windows)

Installation

To install Pretty Logs, you'll need Go 1.23.3 or later. You can build the binary using one of the following methods:

Building from Source

Clone the repository and build using Make:

git clone https://github.com/mrfoh/pretty-logs.git
cd pretty-logs
make build

The binary will be available in the bin directory.

Cross-Platform Builds

The project includes Make targets for various platforms:

• Linux (AMD64): make build-linux
• Linux (ARM64): make build-linux-arm
• macOS (AMD64): make build-macos
• macOS (ARM64): make build-macos-arm
• macOS (Universal): make build-macos-universal

Usage

Pretty Logs reads JSON log input from stdin and outputs formatted logs to stdout. Here's the basic usage:

cat logfile.json | prettylogs [flags]

Command Line Flags

The tool provides numerous flags to customize its behavior:

• -F, --formatTemplateFile: Specify a custom template file for log formatting
• -f, --timestampFormat: Set the timestamp format (default: "2006-01-02 15:04:05.000")
• -L, --levelKey: Specify the key for log level (default: "level")
• -t, --timeKey: Specify the key for timestamp (default: "time")
• -p, --pidKey: Specify the key for process ID (default: "pid")
• -n, --nameKey: Specify the key for application name (default: "name")
• -c, --contextKey: Specify the key for context (default: "context")
• -m, --msgKey: Specify the key for message (default: "msg")
• -k, --errorLikeObjectKeys: Specify keys for error objects (default: ["err", "error"])
• -H, --hostnameKey: Specify the key for hostname (default: "hostname")
• -r, --requestKey: Specify the key for request objects (default: "req")
• -R, --responseKey: Specify the key for response objects (default: "res")

Example Usage

Basic usage with default settings:

tail -f application.log | prettylogs

Using custom field mappings:

cat logs.json | prettylogs --levelKey severity --timeKey timestamp --msgKey message

Using a custom format template:

cat logs.json | prettylogs -F my_template.tmpl

Template Format

Pretty Logs supports custom templates for output formatting. Templates use Go's text/template syntax and have access to the following fields:

• {{.Time}}: Formatted timestamp
• {{.Level}}: Log level
• {{.Pid}}: Process ID
• {{.Name}}: Application name
• {{.Context}}: Log context
• {{.Msg}}: Log message
• {{.Error}}: Error message (if present)
• {{.Req}}: Request object (if present)
• {{.Hostname}}: Hostname

Contributing

Contributions are welcome! Please feel free to submit pull requests. Before submitting, ensure:

1. Your code passes all tests (make test)
2. Your code passes the linter (make lint)
3. You've added tests for new features
4. You've updated documentation as needed

License

This project is licensed under the MIT License - see the LICENSE file for details.