LogNav

A fast, keyboard-driven terminal log viewer built in Rust.

Table of Contents

• Why LogNav?
• Installation
• Getting Started
• Features
  • Navigation
  • Filter by Severity
  • Search
  • Date Filter
  • Exclude Filters
  • Alert Keywords
  • Multi-line Entries
  • Bookmarks
  • Jump to Errors and Warnings
  • Live Mode
  • Merge Multiple Files
  • Cluster Detection
  • Statistics Dashboard
  • Export
  • Themes
  • Command Palette
• Supported Log Formats
  • Custom Formats
• Key Reference
• License

Why LogNav?

Debugging means digging through logs. Traditional tools force you to juggle multiple programs — tail -f for live output, grep for patterns, less for scrolling. LogNav combines all of this into one fast binary with vim-style navigation. Errors are colored red so they jump out. Filters update instantly. New lines stream in without losing your place.

Installation

Windows (winget):

winget install Feho.LogNav

Any platform (crates.io):

cargo install lognav

From source:

cargo install --path .       # from a local checkout

cargo build --release        # or build manually
# Binary: target/release/lognav

Building from source requires Rust 1.85+ (Edition 2024).

Getting Started

lognav /path/to/app.log   # Open a file directly
lognav                    # Launch and open with 'o'

LogNav auto-detects the log format and starts displaying entries.

Features

Navigation

Navigate logs like vim:

Key	Action
j / k	Move down / up
g / G	Top / bottom
h / l	Scroll left / right (wrap off)
PageUp / PageDown	Page navigation

Mouse scrolling and clicking also work.

Filter by Severity

Log entries are color-coded by level. Press a number key to toggle that level:

Level	Key
Error	1
Warn	2
Info	3
Debug	4
Trace	5
Profile	6

Press 0 to reset all levels to visible.

Search

Press / or Ctrl+F to open the search bar. Type a term, press Enter to show all matches in a side panel. Use n / N to jump between matches. Press Ctrl+R to toggle regex mode.

Date Filter

Press Ctrl+D to open the date filter dialog.

Quick filters (press 1–6):

1. Last hour
2. Last 24 hours
3. Today
4. Yesterday
5. Last 7 days
6. Clear filter

Custom range: Tab to the From/To fields and enter relative times (-2h, -30m, -7d), specific dates (2024-03-15 14:00), or keywords (today, yesterday, now).

Exclude Filters

Press x to open the exclude filter manager. Type a pattern and press Enter to hide all matching entries. Ctrl+R toggles regex mode. Press X to clear all exclude filters at once.

Quick exclude: Alt+Click on any word to instantly exclude it.

Alert Keywords

Press ! to open the alert keywords manager. Add patterns that trigger a terminal bell when matched during live mode and highlight them with distinct colors — useful for getting notified about specific errors or events without watching the screen. Ctrl+R toggles regex mode.

Multi-line Entries

Some entries span multiple lines (stack traces, JSON payloads). These appear collapsed by default.

Key	Action
Enter	Expand/collapse selected entry
a	Toggle expand all
d	Detail popup (full-screen view)

Embedded JSON is automatically pretty-printed when expanded.

Bookmarks

Key	Action
m	Toggle bookmark on current line
b / B	Next / previous bookmark

Bookmarks persist across sessions.

Jump to Errors and Warnings

Key	Action
e / E	Next / previous error
w / W	Next / previous warning

Live Mode

Press t to toggle live mode — new entries appear and the view auto-scrolls. Live mode pauses automatically when you scroll up and resumes when you return to the bottom.

Merge Multiple Files

Press M to merge an additional file into the current view. Entries are sorted by timestamp; each source file gets a distinct color indicator.

Cluster Detection

Open via the command palette (Ctrl+P → "Find repeating patterns"). LogNav scans the filtered log for repeating patterns — identical lines or multi-line sequences that appear 3+ times. Variable parts (UUIDs, hex strings, numbers, quoted strings) are replaced with placeholders so near-identical entries cluster together. Useful for spotting noisy repeated errors or identifying startup sequences in a busy log.

Statistics Dashboard

Press F2 to open a statistics overlay showing entry counts, error rate, level distribution, and an event rate timeline.

Timeline controls:

Key	Action
+ / -	Zoom in / out
h / l or ← / →	Pan left / right
Home / End	Jump to start / end
0	Reset zoom and pan
e	Export as HTML

The HTML export includes interactive Chart.js charts with drag-to-zoom and print-friendly styling.

Export

Press Ctrl+S to export the currently filtered entries to a file. Only entries visible after all active filters are exported.

Themes

Open via the command palette (Ctrl+P → "Change theme..."). 12 built-in Dark & Light themes. Selection persists across sessions.

For per-color overrides, edit ~/.config/lognav/config.toml directly. Colors accept named values ("Red"), hex ("#ff0000"), or 256-color index ("238").

Command Palette

Press Ctrl+P to fuzzy-search all available commands. The fastest way to discover features.

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Supported Log Formats

LogNav auto-detects the format from file content. If no known format matches, it falls back to a generic parser that learns level tokens from a sample of lines.

Custom Formats

Define your own format by adding a TOML file to:

• Linux/macOS: ~/.config/lognav/formats/
• Windows: C:\Users\<user>\AppData\Roaming\lognav\config\formats\

name = "myapp"
pattern = '^(?P<level>VRB|DBG|INF|WRN|ERR)\s+(?P<timestamp>\d{4}-\d{2}-\d{2}\s+\d{2}:\d{2}:\d{2}\.\d{3})\s+\S+\s+(?P<message>.*)'
timestamp_format = "%Y-%m-%d %H:%M:%S%.3f"
timezone = "+01:00"

[level_map]
"VRB" = "trace"
"DBG" = "debug"
"INF" = "info"
"WRN" = "warn"
"ERR" = "error"

Named groups:

• level — matched against level_map first, then standard names
• timestamp — parsed with timestamp_format; time-only formats use today's date
• message — if present, used as the message start offset; otherwise message starts after the full match

Custom parsers are loaded automatically on startup and detected at 0.9 confidence.

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Key Reference

Normal Mode

Key	Action
j / k	Move down / up
g / G	Top / bottom
h / l	Scroll left / right
PageUp / PageDown	Page navigation
/ or Ctrl+F	Search
n / N	Next / previous match
1–6	Toggle log levels
0	Reset level filters
Ctrl+D	Date filter
x	Exclude filter manager
X	Clear exclude filters
!	Alert keywords manager
t	Toggle live mode
Alt+W	Toggle word wrap
s	Toggle syntax highlighting
Enter	Expand/collapse entry
a	Toggle expand all
d	Detail popup
m	Toggle bookmark
b / B	Next / previous bookmark
e / E	Next / previous error
w / W	Next / previous warning
c	Copy entry to clipboard
o or Ctrl+O	Open file
M	Merge file
Ctrl+S	Export filtered results
F2	Statistics dashboard
Ctrl+P	Command palette
? or F1	Help
q	Quit

Search Mode

Key	Action
Enter	Apply search
Esc	Cancel
Ctrl+R	Toggle regex
Up / Down	Search history
Ctrl+U	Clear input

Mouse

Action	Effect
Click	Select entry
Scroll	Navigate up/down
Ctrl+Click	Search for word under cursor
Alt+Click	Exclude word under cursor

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License

Licensed under either of Apache License, Version 2.0 or MIT license at your option.