O que significa */5 em uma expressão cron?

A sintaxe */5 significa a cada 5 unidades. No campo dos minutos, */5 significa que o job executa nos minutos 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50 e 55 — essencialmente a cada 5 minutos. Você pode usar isso em qualquer campo: */2 no campo das horas executa a cada 2 horas, */3 no campo do mês executa a cada 3 meses, e assim por diante.

O cron executa nos fins de semana?

Por padrão, sim — a menos que você o restrinja. Uma expressão cron como * * * * * executa a cada minuto, todos os dias, incluindo fins de semana. Para restrição de um trabalho apenas aos dias úteis, use 1-5 no campo dia da semana: 0 9 * * 1-5 executa às 9h de segunda-feira a sexta-feira apenas.

Por que meu job cron não está sendo executado?

Several common reasons: (1) The syntax is wrong — use a cron expression generator to validate it. (2) The job is running but failing silently — check your logs or redirect output with >> /var/log/myjob.log 2>&1. (3) Timezone mismatch — your server may be in UTC while you scheduled for local time. (4) The cron daemon is not running — check with systemctl status cron or service cron status. (5) Environment variables — cron runs with a minimal environment, so paths that work in your shell may not work in cron.

Qual a diferença entre cron e crontab?

Cron é o daemon (serviço em segundo plano) que lê e executa tarefas agendadas. Um crontab (tabela de cron) é o arquivo de configuração que define essas tarefas. Você edita seu crontab com crontab -e e o cron o lê automaticamente. Crontabs sistêmicos estão em /etc/cron.d/ e /etc/crontab; os crontabs dos usuários são armazenados por usuário.

Posso usar um gerador de expressão cron para CronJobs do Kubernetes?

Sim. Os CronJobs do Kubernetes utilizam a mesma sintaxe cron de 5 campos que o cron tradicional do Unix. Uma expressão que funciona no crontab funcionará no especificador de CronJob do Kubernetes. A única diferença é que os CronJobs do Kubernetes têm sua própria configuração de fuso horário no especificador (usando o campo timeZone nas versões mais recentes), então você não está limitado ao fuso horário local do cluster.

Anúncios incomodam? Ir Sem anúncios Hoje 

Pare de buscar sintaxe de Cron — há um gerador para isso

Atualizado em Abr 20, 2026

As expressões cron são um desses itens que você usa constantemente, mas raramente consiga memorizar. Aqui está o que realmente significa cada um dos cinco campos, os erros que afetam as pessoas e por que um gerador de expressão cron on-line é a abordagem mais inteligente.

Stop Googling Cron Syntax — There's a Generator for That 1

ANUNCIADO Remover?

It’s 2am. A deployment is scheduled for 6am. You need to double-check that the cron job will actually fire at the right time. So you open a new tab and type “cron syntax” into Google. Again.

This is a rite of passage. Every developer who has ever touched a Linux server has done it at least once — and most of us have done it more times than we care to admit. Cron expressions are one of those things you use constantly but never quite retain. The syntax sits in an uncomfortable zone between “too simple to look up” and “just specific enough to get wrong.”

There’s a better way. Use a cron expression generator online and let the tool handle the syntax while you focus on what actually matters.

Why Cron Syntax Refuses to Stick

Cron has five fields. Five. That’s it. And yet the order trips people up every single time:

# ┌───────────── minute (0–59)
# │ ┌───────────── hour (0–23)
# │ │ ┌───────────── day of month (1–31)
# │ │ │ ┌───────────── month (1–12)
# │ │ │ │ ┌───────────── day of week (0–6, Sunday=0)
# │ │ │ │ │
  * * * * * command

The problem isn’t that it’s hard — it’s that there are just enough special characters to introduce ambiguity. Is */5 “every 5 minutes” or “at minute 5”? Does 0 9 * * 1-5 run at 9am or 9pm? What happens if you forget that months are 1-indexed but weekdays start at 0?

These aren’t gotchas for beginners. They’re gotchas for everyone. A misconfigured cron job is one of the quieter ways to introduce a production incident — the kind where nothing crashes immediately, it just silently doesn’t run, and you only notice three days later.

The Five Fields, Explained Without Ceremony

Here’s the practical version:

Minute (0–59) — The minute of the hour when the job runs. 30 means the 30-minute mark. */15 means every 15 minutes.
Hour (0–23) — Uses 24-hour time. 9 is 9am. 17 is 5pm. No AM/PM nonsense.
Day of month (1–31) — Which calendar day. 1 is the first of the month. 15 is the 15th.
Month (1–12) — January is 1, December is 12. You can also use names: JAN, FEB, etc.
Day of week (0–6 or 1–7) — Sunday can be 0 ou 7 depending on your cron implementation. Monday is always 1. This is the field that causes the most confusion.

The Special Characters That Matter

* — Every possible value (every minute, every hour, etc.)
*/n — Every nth interval. */5 in the minute field means every 5 minutes.
a-b — A range. 1-5 in the weekday field means Monday through Friday.
a,b,c — A list. 1,3,5 means Monday, Wednesday, Friday.
@reboot, @hourly, @daily — Shorthand aliases. Not supported everywhere.

Common Mistakes That Bite People

1. Forgetting Timezone

Cron runs in the server’s local timezone. If your server is UTC and you’re in New York, 0 9 * * * does not run at 9am Eastern — it runs at 4am or 5am, depending on DST. Always know your server timezone. Always.

2. Using Both Day-of-Month and Day-of-Week

If you specify a value in both the day-of-month e day-of-week fields (instead of * in one of them), most cron implementations treat it as an OR — the job runs when either condition matches. That’s almost never what you want.

3. Expecting */1 to Mean “Once”

*/1 is the same as *. It means “every.” There is no way to express “run once” in standard cron — for that, you’d use at or a one-shot systemd timer.

4. Not Testing Before Deploying

Cron gives you no immediate feedback. You write the expression, save the crontab, and then wait. If it’s wrong, you find out at 3am when the scheduled backup doesn’t run. This is why using a cron next run calculator before you deploy is worth the 30 seconds it takes.

Use a Cron Expression Generator Instead

The honest advice: stop trying to hand-write cron expressions from memory. Use a generator. It’s not a sign of weakness — it’s how you avoid dumb mistakes in production.

O cron expression generator on IOTools lets you build any expression visually — pick your minute interval, hour, day of week, and it shows you the exact expression and a plain-English explanation of when it runs. No memorization required, no documentation tabs open.

Once you have an expression, run it through the cron next run calculator. Paste the expression, get back the next 5–10 scheduled execution times. It takes five seconds and will tell you immediately if you’ve accidentally scheduled your cleanup job to run every minute instead of once a day.

That second check is the one most people skip. Don’t skip it.

Quick Reference: Expressions You’ll Actually Use

Expression	Significado
`* * * * *`	A cada minuto
`0 * * * *`	Every hour, on the hour
`0 9 * * *`	Every day at 9:00am
`0 9 * * 1-5`	Weekdays at 9:00am
`/15 * * *`	A cada 15 minutos
`0 0 * * 0`	Every Sunday at midnight
`0 0 1 * *`	First day of every month at midnight
`30 4 1,15 * *`	1st and 15th of the month at 4:30am
`0 22 * * 1-5`	Weekdays at 10:00pm
`@daily`	Once per day at midnight (shorthand)