A comprehensive utility to validate cron syntax, generate human-readable explanations, and calculate upcoming execution schedules.
Install & Download
1. ClawHub CLI
The fastest way to install a skill directly from the registry.
npx clawhub@latest install crontab-validator
2. Manual Installation
Copy the skill folder to one of these locations
~/.openclaw/skills/ <project>/skills/ Priority: Workspace > Local > Bundled
3. Prompt Installation
Copy this prompt to OpenClaw to install it automatically.
Help me install crontab-validator using Clawhub. If Clawhub is not installed, install it first (npm i -g clawhub).
Prefer to download?
Get the raw skill files in a ZIP archive.
What is Crontab Validator?
Crontab Validator is a specialized tool designed to demystify complex cron schedules. It provides developers with a robust environment to lint expressions for common logical errors and verify execution patterns before they hit production servers. By integrating this utility into your workflow via Openclaw Skills, you can ensure that scheduled tasks behave exactly as intended, reducing the risk of downtime or unexpected high-frequency execution.
Beyond simple validation, the tool offers deep analysis of crontab entries, converting cryptic syntax into plain English explanations. It supports standard cron formats, range/step combinations, and common shortcuts like @daily or @monthly. Whether you are debugging a legacy crontab or architecting new automation, this skill provides the technical precision required for modern DevOps environments.
Crontab Validator Use Cases
- Verifying the syntax of complex cron expressions to prevent deployment failures.
- Translating cryptic cron strings into human-readable descriptions for documentation.
- Identifying logical errors such as scheduling day 31 for months with only 30 days.
- Predicting the next 5 to 10 run times to align task execution with maintenance windows.
- Auditing high-frequency tasks that may put unnecessary load on system resources.
How Crontab Validator Works
- The user provides a cron expression or shortcut via the command line or agent interface.
- The system parses the five or six-field cron format, identifying wildcards, ranges, steps, and specific values.
- A validation engine checks for structural integrity and legal value ranges for minutes, hours, days, and months.
- If linting is enabled, the tool performs heuristic checks for common pitfalls like high-frequency intervals or impossible dates.
- The tool generates the requested output, which can include a natural language explanation, a list of upcoming timestamps, or a JSON/Markdown report.
Crontab Validator Setup
To use this tool within the Openclaw Skills framework, ensure you have Python 3 installed. Clone the repository and run the scripts directly:
# Validate a specific cron expression
python3 scripts/cron_check.py validate "*/15 * * * *"
# Explain a complex schedule
python3 scripts/cron_check.py explain "30 4 1,15 * 1-5"
Crontab Validator Data Schema & Taxonomy
The skill processes input strings and returns structured data. Users can specify the output format using the -f flag:
| Attribute | Description |
|---|---|
| Status | Success/Failure of the syntax validation |
| Explanation | Human-readable string describing the schedule |
| Next Runs | Array of ISO 8601 timestamps for upcoming executions |
| Lint Warnings | Information regarding potential logic errors (e.g., Every-minute warnings) |
Supported output formats include text, json, and markdown for seamless integration into other Openclaw Skills workflows.
Crontab Validator Advanced Features
- Strict Mode: Enable --strict to force non-zero exit codes on linting warnings, ideal for CI/CD pipelines.
- Custom Run-time Calculation: Use --from-time to calculate next execution cycles starting from a specific future or past date.
- Multi-expression Linting: Batch process multiple cron entries in a single command to audit entire crontab files.
- Shortcut Support: Full compatibility with @yearly, @monthly, @weekly, @daily, and @hourly macros.
SKILL.md
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