ch - Colored Highlighter

A fast, simple terminal tool to highlight specific words in your command output with colors. Perfect for tailing logs, debugging, and making command output more readable.

Features

• Automatic color assignment from a preset palette
• Custom hex colors for specific words
• Case-insensitive matching by default
• Whole word extension mode
• Fast and efficient - designed for real-time log tailing
• Cross-platform - works on macOS and Linux

How It Works

ch reads from standard input line by line and:

1. Searches for specified words (case-insensitive by default)
2. Highlights matches with assigned colors
3. Handles overlapping matches (first match wins)
4. Outputs to standard output with ANSI color codes

The preset colors use a pastel palette optimized for readability on both light and dark terminals: Red, Green, Orange, Blue, Pink, Purple.
Colors cycle when you have more than 6 words without custom colors.

The tool is optimized for streaming, making it ideal for real-time log monitoring.

Usage

Basic syntax

ch [options] <word1> <word2> <word3> ...

Highlights specified words with colors from a preset palette.

Custom colors

ch <word1>::<HEXCOLOR> <word2>::<COLORNAME> <word3> ...

Use custom hex colors (with or without # prefix) or named colors. Words without specified colors use preset colors.

Available named colors: red, green, orange, blue, pink, purple

Options

• -s - Case-sensitive matching (default is case-insensitive)
• -w - Whole word extension - extends match until space or end of line
• -b - Use background colors instead of foreground colors
• -a - Play a discreet beep when a match is found

Case-sensitive matching

# Only highlights exact case matches
echo "Error ERROR error" | ch -s Error

Whole word extension

The -w flag extends the match to the entire word (until space or EOL):

# Input: "Notice: backup 13344 - started with name backup_13344.zip"
echo "Notice: backup 13344 - started with name backup_13344.zip" | ch -w back

# Highlights: "backup" and "backup_13344.zip" (entire words)

Background colors

The -b flag uses background colors instead of foreground colors:

# Highlight with background colors
tail -f app.log | ch -b error warning success

# Mix with custom colors
tail -f app.log | ch -b error::red warning::orange info::blue

Audible alert

The -a flag plays a discreet beep when a match is found; the alert is not even if matches are frequent (max one every 5 seconds):

# Play a beep
tail -f app.log | ch -a panic::red

# Test repeated match heads with a one-second interval
for i in {1..10}; do echo "line $i"; sleep 1; echo "error occurred"; sleep 1; done | ch -a error

Examples

Log monitoring

# Tail a log file with highlighted keywords
tail -f app.log | ch error warning success

# Highlight with custom colors (hex and named)
tail -f app.log | ch error::red warning::orange info::00FF00

# Monitor system logs
journalctl -f | ch failed::red error::red success::green started::blue

# Watch Docker logs
docker logs -f container_name | ch error warning started stopped

# Monitor Kubernetes pods
kubectl logs -f pod-name | ch error panic fatal warning

Database and queries

# Highlight database queries
tail -f query.log | ch SELECT INSERT UPDATE DELETE

# Database monitoring
mysql -e "SHOW PROCESSLIST;" | ch SELECT UPDATE DELETE INSERT

Development and debugging

# Search and highlight
grep -i "error" app.log | ch error exception failed

# Highlight build output
make 2>&1 | ch error warning success completed

# Git log highlighting
git log --oneline | ch feat fix docs style refactor

# Highlight code patterns
cat script.sh | ch function if else error

Combining features

# Mix preset, named, and hex colors
tail -f app.log | ch error::red warning::FF5500 info debug success::green

# Case-insensitive by default (highlights: error, Error, ERROR, ErRoR, etc.)
tail -f app.log | ch error

# Monitor web server logs with named colors
tail -f access.log | ch GET::blue POST::orange 404::red 500::red 200::green

Build

From source

# Clone or download the repository
git clone <repository-url>
cd ch

# Initialize Go module
go mod init ch

# Build
go build -o ch

# (Optional) Install to your PATH
sudo mv ch /usr/local/bin/

Buffering issues

Some programs detect when their output is being piped and switch from line buffering to full buffering for performance. This means output may not appear in real-time when using ch. If you experience delayed highlighting or no output until the program completes, you need to force line buffering using one of these methods:

macOS

# Use script (built-in)
script -q /dev/null your-command | ch your-words

# Or install and use unbuffer
brew install expect
unbuffer your-command | ch your-words

Linux

# Use stdbuf (usually built-in)
stdbuf -oL your-command | ch your-words

# Or use script
script -qfc "your-command" /dev/null | ch your-words

# Or install and use unbuffer
unbuffer your-command | ch your-words

Performance

ch uses buffered I/O and processes input line by line, making it efficient for:

• Large log files
• Real-time streaming with tail -f
• High-throughput pipelines
• Continuous monitoring scenarios

Requirements

• Go 1.16 or higher (for building)
• Terminal with ANSI color support (most modern terminals)
• macOS or Linux operating system

License

MIT License - feel free to use and modify as needed.