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SmartLog

A fast, ergonomic terminal UI for tailing and filtering JSON and plain-text logs in real time.

Built with Rust | Async I/O with Tokio | Beautiful TUI with Ratatui

Features

  • Auto-detect log format -- Automatically identifies JSON vs. plain text
  • Pretty-print JSON -- Colorized output with severity-based coloring
  • Live filtering -- Instant substring and regex search with match highlighting
  • Log level filtering -- Cycle through ERROR, WARN, INFO, DEBUG levels
  • Line wrapping -- Toggle wrapping on/off
  • Mouse support -- Scroll with the mouse wheel
  • Follow mode -- Smooth auto-scroll that tracks new log entries
  • File tailing -- tail -f style with truncation and rotation detection
  • Stdin piping -- Pipe any command output: tail -f app.log | smartlog
  • Multi-file tailing -- Watch multiple files simultaneously with source labels
  • Color themes -- Dark, light, solarized, and dracula presets
  • Relative timestamps -- See how long ago each log entry was written
  • Log export -- Save filtered logs to files
  • Debug logging -- Built-in diagnostics for troubleshooting SmartLog itself
  • Shell completions -- Tab completion for bash, zsh, fish, elvish, powershell
  • Graceful shutdown -- Terminal state always restored, even on panic

Quick Start

Tail a specific log file:

smartlog --file /var/log/myapp.log

Tail multiple files at once:

smartlog --file /var/log/app.log --file /var/log/error.log

Pipe logs directly:

tail -f /var/log/app.log | smartlog

Run smartlog --help to see all available options.

Log Format Support

JSON Logs

SmartLog automatically detects and pretty-prints JSON with level detection:

{"level": "ERROR", "msg": "Database connection failed", "error_code": 500}

Supported level fields: level, severity, lvl

Level Color
ERROR / ERR / FATAL Red
WARN / WARNING Yellow
INFO / INFORMATION Green
DEBUG / TRACE Blue

Plain Text Logs

For non-JSON logs, SmartLog scans for keywords:

2024-12-13 10:30:45 ERROR Database connection timeout

Keywords: error, fatal, warn, info, debug, trace (case-insensitive)

Performance

  • Async non-blocking streaming -- Logs are processed as they arrive
  • Bounded memory -- Circular buffer of last 2000 entries (configurable)
  • Concurrent I/O -- File tailing and terminal rendering run concurrently
  • Fast JSON parsing -- Powered by serde_json

Reliability

  • Graceful shutdown -- Handles SIGINT (Ctrl+C) and SIGTERM cleanly
  • Terminal restoration -- RAII guard ensures terminal state is always restored
  • File rotation handling -- Automatically detects and recovers from log rotation
  • Error recovery -- Continues running on temporary errors

Troubleshooting

  • If nothing appears when running smartlog without --file, make sure you're piping input (e.g., ... | smartlog). Without piped stdin and no file, SmartLog shows a demo stream.
  • Ensure smartlog has read access to any files you tail.
  • On Windows, make sure your terminal supports VT sequences (Windows 10+).

License

MIT License. See LICENSE for details.

Author

Felipe Pires Morandini