dchk (domain availability check)


A fast, UNIX-style domain availability checker using the RDAP protocol.

Overview

dchk is a command-line tool for checking domain name availability using the Registration Data Access Protocol (RDAP). It provides clean, scriptable output with proper UNIX exit codes, making it perfect for automation and batch processing.

Features

- RDAP Protocol: Uses modern RDAP instead of deprecated WHOIS
- Authoritative Sources: Queries authoritative RDAP servers directly
- Concurrent Processing: Check multiple domains simultaneously
- UNIX-Style: Proper exit codes and clean output for scripting
- Flexible Input: Command-line arguments or stdin pipeline
- Detailed Output: Optional verbose mode with response times and sources
- Timeout Handling: Configurable timeouts with graceful error handling

Installation

$3

``bash
npm install -g dchk
`

Usage

$3

Check a single domain:
`bash
dchk example.com


Output: available

Exit code: 0 (available) or 1 (registered)

`

Check multiple domains:
`bash
dchk google.com facebook.com nonexistent123.com


Output:

google.com: registered

facebook.com: registered

nonexistent123.com: available

`

$3

Get detailed information with response times and sources:
`bash
dchk --verbose google.com facebook.com nonexistent123.com


Output:

DOMAIN STATUS TIME SOURCE

────────────────────────────────────────────

google.com REGISTERED 634ms rdap.verisign.com

facebook.com REGISTERED 521ms rdap.verisign.com

nonexistent123.com AVAILABLE 387ms rdap.org

`

$3

Process domains from stdin:
`bash
echo "example.com" | dchk
cat domains.txt | dchk --verbose
echo "google.com facebook.com" | tr ' ' '\n' | dchk
`

$3

Use exit codes for conditional logic:
`bash
if dchk mydomain.com; then
echo "Domain is available!"
else
echo "Domain is taken or error occurred"
fi
`

Command Line Options

`
Usage: dchk [options] [domains...]

UNIX-style domain availability checker (RDAP-first)

Arguments:
domains domain names to check (also reads from stdin)

Options:
-V, --version output the version number
-v, --verbose enable verbose output with response times and sources
-q, --quiet suppress non-error output
-c, --concurrency maximum concurrent checks (default: "10")
-t, --timeout request timeout in milliseconds (default: "5000")
--no-fallback disable authoritative RDAP fallback
-h, --help display help for command
`

Exit Codes

Following UNIX conventions:

- 0: Domain is available (success)
- 1: Domain is registered (failure)
- 2: Error occurred (invalid domain, network error, etc.)

Examples

$3


`bash
dchk example.com

available (exit code 0)

dchk google.com

registered (exit code 1)

`

$3

`bash

From file

cat domains.txt | dchk --verbose --concurrency 5

From command line

dchk domain1.com domain2.com domain3.com --verbose

Mixed with timeout

dchk --timeout 3000 --verbose example.com test.com
`

$3

`bash
#!/bin/bash

Check if domain is available before proceeding

if dchk "$1" >/dev/null 2>&1; then
echo "Domain $1 is available - proceeding with registration"
# registration logic here
else
echo "Domain $1 is not available"
exit 1
fi
`

$3

`bash

Test with high concurrency

echo "google.com facebook.com twitter.com github.com" | \
tr ' ' '\n' | \
dchk --verbose --concurrency 10 --timeout 2000
`

Output Formats

$3

`
available
registered
unknown
`

$3

`
domain1.com: available
domain2.com: registered
domain3.com: unknown
`

$3

`
DOMAIN STATUS TIME SOURCE
────────────────────────────────────────────
domain1.com AVAILABLE 234ms rdap.org
domain2.com REGISTERED 456ms rdap.verisign.com
`

RDAP Protocol

dchk uses the Registration Data Access Protocol (RDAP), the modern successor to WHOIS:

- Structured Data: JSON responses instead of unstructured text
- Standardized: Consistent format across registries
- Authoritative: Queries official registry sources
- Reliable: Better error handling and status codes

The tool automatically:
1. Queries rdap.org as the primary source
2. Falls back to authoritative RDAP servers via IANA bootstrap
3. Follows HTTP redirects to reach the correct endpoints
4. Handles rate limiting and timeout scenarios

Development

$3

- Node.js >= 20.0.0
- npm or yarn

$3

`bash
git clone https://github.com/carlrannaberg/dchk.git
cd dchk
npm install
`

$3

`bash
npm run build # Build for production
npm run build:watch # Build and watch for changes
`

$3

`bash
npm test # Run all tests
npm run test:unit # Unit tests only
npm run test:integration # Integration tests only
npm run test:e2e # End-to-end tests only
`

$3

`
├── cli/
│ ├── commands/ # Command implementations
│ ├── lib/ # Core RDAP functionality
│ ├── utils/ # Utility functions
│ └── types/ # TypeScript type definitions
├── tests/
│ ├── unit/ # Unit tests
│ ├── integration/ # Integration tests
│ └── e2e/ # End-to-end tests
└── dist/ # Built output
`

Library Usage

dchk can also be used as a library:

`javascript
import { checkDomain, isValidDomain } from 'dchk';

// Check single domain
const result = await checkDomain('example.com');
console.log(result.status); // 'available', 'registered', or 'unknown'

// Validate domain format
if (isValidDomain('example.com')) {
// proceed with check
}
`

Contributing

1. Fork the repository
2. Create a feature branch (git checkout -b feature/amazing-feature)
3. Make your changes
4. Add tests for new functionality
5. Ensure all tests pass (npm test)
6. Commit your changes (git commit -m 'Add amazing feature')
7. Push to the branch (git push origin feature/amazing-feature)
8. Open a Pull Request

License

MIT License - see LICENSE file for details.

Related Tools

- whois - Traditional WHOIS client
- dig - DNS lookup utility
- nslookup - DNS query tool
- host - DNS lookup utility

dchk` complements these tools by providing modern RDAP-based domain availability checking with clean, automatable output.