Scheduler

Utah provides built-in cron scheduling to install recurring jobs directly from your scripts.

scheduler.cron()

Registers a cron job that runs on the specified schedule. The job body is written as a lambda function.

scheduler.cron("CRON_PATTERN", () => {
  // Job body
});

Parameters:

Parameter	Type	Description
cronPattern	string	Standard 5-field cron expression (minute hour day month weekday)
job	lambda	Lambda function containing the code to run on each invocation

Cron Pattern Reference

Field	Allowed Values	Special Characters
Minute	0–59	* , - /
Hour	0–23	* , - /
Day of month	1–31	* , - /
Month	1–12	* , - /
Day of week	0–7 (0 and 7 = Sunday)	* , - /

Examples

Run Every 6 Hours

scheduler.cron("0 */6 * * *", () => {
  console.log("Running every 6 hours...");
  console.log("Performing maintenance tasks...");
});

Daily at Midnight

scheduler.cron("0 0 * * *", () => {
  console.log("Daily maintenance");
  console.log("Cleaning up temporary files...");
});

Weekly on Monday at 2 AM

scheduler.cron("0 2 * * 1", () => {
  console.log("Weekly report generation");
  let reportDate: string = "Monday Report";
  console.log("Generating: ${reportDate}");
});

Complete Script with Multiple Jobs

script.description("Maintenance scheduler");

console.log("Setting up scheduled tasks...");

scheduler.cron("0 */6 * * *", () => {
  console.log("Running every 6 hours...");
  console.log("Performing maintenance tasks...");
});

scheduler.cron("0 0 * * *", () => {
  console.log("Daily maintenance");
  console.log("Cleaning up temporary files...");
});

scheduler.cron("0 2 * * 1", () => {
  console.log("Weekly report generation");
  let reportDate: string = "Monday Report";
  console.log("Generating: ${reportDate}");
});

console.log("Scheduler setup complete!");

Generated Bash

Each scheduler.cron() call compiles to bash that:

1. Creates a ~/.utah/cron/ directory for job scripts
2. Writes the lambda body into a standalone executable script
3. Checks for duplicate cron entries before installing
4. Registers the job via crontab

# Create Utah cron directory
_utah_cron_dir="$HOME/.utah/cron"
mkdir -p "${_utah_cron_dir}"
_utah_cron_script="${_utah_cron_dir}/job_$(date +%s)_$$.sh"

# Generate the cron job script
cat > "${_utah_cron_script}" << 'EOF'
#!/bin/bash
# Generated by Utah - scheduler.cron("0 */6 * * *")
echo "Running every 6 hours..."
echo "Performing maintenance tasks..."
EOF

# Make the script executable
chmod +x "${_utah_cron_script}"

# Check if similar cron job already exists
_utah_cron_pattern="0 \*/6 \* \* \*.*utah.*job_"
if ! crontab -l 2>/dev/null | grep -q "${_utah_cron_pattern}"; then
    # Add to crontab
    (crontab -l 2>/dev/null; echo "0 */6 * * * ${_utah_cron_script}") | crontab -
    echo "Cron job installed: 0 */6 * * * ${_utah_cron_script}"
else
    echo "Similar cron job already exists"
fi

Behavior

• Duplicate detection: Before installing, Utah checks the existing crontab for a matching pattern. If a similar job already exists, it prints a message and skips installation.
• Job storage: Generated scripts are stored under ~/.utah/cron/ with unique filenames using timestamp and PID (job_<epoch>_<pid>.sh).
• Lambda compilation: Variables and statements inside the lambda are compiled to bash as if they were top-level code in the generated script.
• Idempotent execution: Running the same script multiple times will not create duplicate cron entries.

Common Cron Patterns

Pattern	Description
* * * * *	Every minute
0 * * * *	Every hour
0 */6 * * *	Every 6 hours
0 0 * * *	Daily at midnight
0 0 * * 0	Weekly on Sunday at midnight
0 2 * * 1	Monday at 2 AM
0 0 1 * *	First day of every month
*/5 * * * *	Every 5 minutes
0 9-17 * * 1-5	Hourly during business hours (Mon–Fri)