umber

A modern replacement for cat with syntax highlighting and automatic language detection.

Features

• Syntax highlighting for 100+ languages using tree-sitter parsers
• Automatic language detection based on file extension and content
• Line numbers with --style=numbers
• Git change indicators showing added, modified, and removed lines with --style=changes
• Rich highlighting (language injections / embedded languages) with --style=rich
• Show unprintable characters with -A / --show-all (tabs as →, carriage returns as ↵, etc.) - unlike bat, syntax highlighting is preserved!
• Theme support with automatic dark/light mode detection
• Stdin support for piping commands
• Fast - built with Rust and tree-sitter
• Shell completions for bash, zsh, fish, and more

Installation

From source

cargo install --path .

Or using mise (recommended for development):

mise install
mise build:debug

Usage

Getting help

# Quick help
umber -h

# Detailed help with examples
umber --help

# View man page (after installation)
man umber

Basic usage

Display a file with syntax highlighting:

umber main.rs

Display multiple files:

umber main.rs lib.rs

Show unprintable characters (tabs as →, line feeds as ␊):

umber -A main.rs

Read from stdin:

echo 'fn main() { println!("Hello!"); }' | umber
# or explicitly:
cat main.rs | umber -

Line numbers

Show line numbers with the numbers style component:

umber --style=numbers main.rs

Decorations (line numbers, git changes)

Control which decorations to display with the --style flag:

# Show line numbers with grid separator
umber --style=numbers main.rs

# Show git change indicators (+, ~, -)
umber --style=changes main.rs

# Combine multiple decorations
umber --style=numbers,changes main.rs

# Enable richer highlighting (language injections / embedded languages)
umber --style=rich main.rs

Note: --style=rich can be significantly slower on very large files.

Git change indicators show:

• + (green) - added lines
• ~ (yellow) - modified lines
• - (red) - removed lines

Show unprintable characters

Display tabs, carriage returns, line feeds, and other non-printable characters with -A / --show-all:

umber -A main.rs

This shows:

• · (middle dot) for spaces
• → (right arrow) for tabs
• ␊ (line feed symbol) at the end of lines
• ↵ (carriage return symbol) for \r
• ␛ (escape symbol) for escape characters
• ␀, ␁, ␂, etc. for other control characters

Unlike bat -A, umber maintains full syntax highlighting while showing unprintable characters!

# Combine with line numbers
umber -A -n main.rs

# Works with git change indicators too
umber -A --style=changes,numbers main.rs

Language override

Force a specific language when auto-detection fails:

umber --language rust config.txt
umber --language json response.log

To see all supported languages, check the syntastica documentation.

Themes

Specify a theme with --theme:

umber --theme dracula main.rs
umber --theme gruvbox-light main.rs

By default, umber uses auto which detects your system's dark/light mode preference:

• Light mode: Catppuccin Latte
• Dark mode: Catppuccin Mocha

Available themes

See the full list of themes in the syntastica-themes documentation.

Popular themes include:

• dracula
• gruvbox-dark / gruvbox-light
• nord
• one-dark / one-light
• catppuccin-mocha / catppuccin-latte / catppuccin-frappe / catppuccin-macchiato
• solarized-dark / solarized-light
• tokyo-night

Shell completions

Generate shell completions for your shell:

# Bash
umber --completions bash > ~/.local/share/bash-completion/completions/umber

# Zsh
umber --completions zsh > ~/.zsh/completion/_umber

# Fish
umber --completions fish > ~/.config/fish/completions/umber.fish

# PowerShell
umber --completions powershell > umber.ps1

Man page

Generate and install a man page:

# Generate man page
umber --man-page > umber.1

# Install system-wide (requires sudo)
sudo cp umber.1 /usr/local/share/man/man1/

# View the man page
man umber

Examples

# View a Rust file with line numbers
umber --style=numbers src/main.rs

# View JSON with syntax highlighting
umber package.json

# Pipe git diff through umber
git diff | umber --language diff

# Compare files side by side with syntax highlighting
diff <(umber file1.js) <(umber file2.js)

# View logs with Python syntax highlighting
umber --language python app.log

# Use a specific theme
umber --theme nord config.yaml

# View multiple files with line numbers
umber --style=numbers *.rs

# Show unprintable characters (tabs, line feeds, etc.) with syntax highlighting
umber -A main.rs

# Debug a file with mixed line endings
umber -A --style=numbers problem_file.txt

Supported Languages

umber supports 100+ programming languages through tree-sitter parsers, including:

• C, C++, C#, Objective-C
• Rust, Go, Zig
• JavaScript, TypeScript, JSX, TSX
• Python, Ruby, Perl, PHP
• Java, Kotlin, Scala
• Swift, Dart
• HTML, CSS, SCSS, Vue
• Bash, Fish, PowerShell
• SQL, GraphQL
• YAML, TOML, JSON, XML
• Markdown, reStructuredText
• And many more...

For a complete list, see the syntastica-parsers documentation.

Why umber?

• Modern syntax highlighting using tree-sitter for accurate, grammar-aware highlighting
• Show unprintable characters with colors - unique feature that maintains highlighting while showing tabs, line feeds, and control characters
• Smart defaults with automatic theme and language detection
• Familiar interface - works just like cat but with colors
• Fast and reliable - built with Rust for performance and safety
• No configuration needed - works out of the box with sensible defaults

Comparison with other tools

Feature	umber	bat	ccat	highlight
Syntax highlighting	✅ Tree-sitter	✅ syntect	✅ pygments	✅
Auto language detection	✅	✅	✅	✅
Line numbers	✅	✅	❌	✅
Themes	✅ Many	✅ Many	✅ Few	✅ Many
Git integration	✅	✅	❌	❌
Show unprintable chars	✅ with colors	✅ no colors	❌	❌
Paging	❌	✅	❌	❌
Binary files	❌	✅	❌	❌

Key difference: umber shows unprintable characters (tabs, line feeds, control chars) while maintaining syntax highlighting - unlike bat -A which disables colors.

umber focuses on being a simple, fast cat replacement with excellent syntax highlighting and git change indicators. If you need features like a built-in pager or binary file detection, check out bat.

Development

This project uses mise for development:

# Install dependencies
mise install

# Build
mise build:debug

# Run tests
mise test

# Format code
mise format

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

License

MIT License - see LICENSE file for details.

Acknowledgments

• syntastica - Syntax highlighting library
• tree-sitter - Parser generator tool
• clap - Command line argument parser