Cron Expression: Every Minute Between 9 AM and 5 PM (* 9-17 * * *)

The cron expression * 9-17 * * * executes a task every minute during business hours (9 AM to 5 PM), making it ideal for real-time monitoring, health checks, and tasks that need frequent execution during work hours.

Expression Breakdown

* 9-17 * * *
│ │   │ │ │
│ │   │ │ └─── Day of week: * (every day)
│ │   │ └───── Month: * (every month)
│ │   └─────── Day of month: * (every day)
│ └─────────── Hour: 9-17 (9 AM to 5 PM)
└───────────── Minute: * (every minute)

Field Values

Range Syntax

The 9-17 in the hour field is a range that means "hours 9 through 17":

• Runs every minute from 09:00 to 17:59
• Total: 9 hours × 60 minutes = 540 executions per day

Execution Time

This expression runs 540 times per day during:

• Every minute from 9:00 AM to 5:59 PM

Common Use Cases

1. Real-Time Monitoring

* 9-17 * * * /usr/local/bin/real-time-monitor.sh

Monitor system health, application status, or service availability during business hours.

2. Queue Processing

* 9-17 * * * /usr/bin/node /app/process-queue.js

Process job queues or message queues continuously during business hours.

3. Health Checks

* 9-17 * * * /usr/local/bin/health-check.sh

Perform frequent health checks on critical services during work hours.

4. Data Collection

* 9-17 * * * /usr/bin/python3 /scripts/collect-metrics.py

Collect real-time metrics, logs, or sensor data during business hours.

Example Implementations

Real-Time Monitor Script

#!/bin/bash
# /usr/local/bin/real-time-monitor.sh

LOG_FILE="/var/log/realtime-monitor.log"
THRESHOLD_CPU=85
THRESHOLD_MEM=90

CPU_USAGE=$(top -bn1 | grep "Cpu(s)" | awk '{print $2}' | cut -d'%' -f1)
MEM_USAGE=$(free | grep Mem | awk '{printf "%.0f", $3/$2 * 100}')

if (( $(echo "$CPU_USAGE > $THRESHOLD_CPU" | bc -l) )); then
    echo "$(date): WARNING - CPU usage at ${CPU_USAGE}%" >> $LOG_FILE
fi

if [ $MEM_USAGE -gt $THRESHOLD_MEM ]; then
    echo "$(date): WARNING - Memory usage at ${MEM_USAGE}%" >> $LOG_FILE
fi

Best Practices

1. Resource Usage: Every-minute execution is resource-intensive; keep tasks lightweight
2. Execution Time: Tasks must complete within 30-40 seconds to avoid overlap
3. Error Handling: Implement comprehensive error handling and logging
4. Idempotency: Ensure tasks can run multiple times safely
5. Monitoring: Track execution time and failures closely

When to Use

✅ Good for:

• Real-time monitoring during business hours
• Frequent health checks
• Queue processing
• Data collection
• Critical service monitoring

❌ Avoid for:

• Heavy computations
• Long-running processes
• Tasks requiring more than 30 seconds
• Operations outside business hours

Related Patterns

Conclusion

The * 9-17 * * * expression is perfect for real-time monitoring and frequent checks during business hours. It provides maximum responsiveness during work hours while avoiding unnecessary execution outside business time, making it ideal for critical monitoring and queue processing during peak usage periods.