Cron Expression Generator

import { CronJob } from 'cron';

// Build a cron expression: every weekday at 9:00 AM
const expression = '0 9 * * 1-5';

const job = new CronJob(expression, () => {
  console.log('Running weekday morning task');
});
job.start();

// Programmatic expression building
function buildCron({ minute = '*', hour = '*', dom = '*', month = '*', dow = '*' }) {
  return `${minute} ${hour} ${dom} ${month} ${dow}`;
}

const expr = buildCron({ minute: '0', hour: '*/6', dow: '1-5' });
console.log(expr); // → "0 */6 * * 1-5"

from crontab import CronTab

# Create a new cron job for the current user
cron = CronTab(user=True)

# Build a job: run backup.py every day at 2:30 AM
job = cron.new(command='python3 /home/user/backup.py')
job.setall('30 2 * * *')

print(job)           # → 30 2 * * * python3 /home/user/backup.py
print(job.is_valid()) # → True

# Schedule every 15 minutes on weekdays
job2 = cron.new(command='/usr/bin/sync-data')
job2.minute.every(15)
job2.dow.during('MON', 'FRI')

cron.write()  # Save to user's crontab

# Verify next run time
from croniter import croniter
from datetime import datetime

it = croniter('30 2 * * *', datetime.now())
print(it.get_next(datetime))  # → next 2:30 AM timestamp

package main

import (
    "fmt"
    "strings"
    "github.com/robfig/cron/v3"
)

// BuildCron constructs a 5-field cron expression from parts
func BuildCron(minute, hour, dom, month, dow string) string {
    fields := []string{minute, hour, dom, month, dow}
    return strings.Join(fields, " ")
}

func main() {
    // Generate: every weekday at 9 AM
    expr := BuildCron("0", "9", "*", "*", "1-5")
    fmt.Println(expr) // → 0 9 * * 1-5

    // Validate and schedule it
    c := cron.New()
    _, err := c.AddFunc(expr, func() {
        fmt.Println("Running scheduled task")
    })
    if err != nil {
        fmt.Printf("Invalid expression: %v\n", err)
        return
    }
    c.Start()
}

# Open the crontab editor to add a new job
crontab -e

# Add a cron job without opening an editor:
# Run cleanup.sh every Sunday at 3 AM
(crontab -l 2>/dev/null; echo "0 3 * * 0 /home/user/cleanup.sh") | crontab -

# Generate and add a job: every 10 minutes, log disk usage
EXPR="*/10 * * * *"
CMD="df -h >> /var/log/disk-usage.log"
(crontab -l 2>/dev/null; echo "$EXPR $CMD") | crontab -

# Verify the job was added
crontab -l | tail -1
# → */10 * * * * df -h >> /var/log/disk-usage.log

# Remove all cron jobs (use with caution)
# crontab -r