Common cron expressions in Linux CLI - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the cron expression 0 0 * * * mean?

It means the task runs every day at midnight (00:00). The fields represent: minute=0, hour=0, every day, every month, every weekday.

beginner

Explain the cron expression */15 * * * *.

This runs a task every 15 minutes. The */15 in the minute field means 'every 15 minutes', while the other fields mean every hour, day, month, and weekday.

intermediate

What does 0 9 * * 1-5 schedule?

It schedules a task to run at 9:00 AM every weekday (Monday to Friday). The 1-5 in the weekday field means Monday through Friday.

intermediate

How do you schedule a cron job to run at 5:30 PM on the 1st of every month?

Use 30 17 1 * *. This means minute=30, hour=17 (5 PM), day=1, every month, every weekday.

intermediate

What does the cron expression 0 0 1 1 * do?

It runs a task once a year at midnight on January 1st. The fields mean: minute=0, hour=0, day=1, month=1 (January), every day of the week.

What does the cron expression 0 * * * * do?

A Runs a task every hour at the start of the hour

B Runs a task every minute

C Runs a task once a day at midnight

D Runs a task every day at noon

The minute field is 0, so it runs at minute 0 of every hour, meaning at the start of every hour.

Which cron expression runs a task every Sunday at 3 AM?

A 0 3 * * 7

B Both A and B

C 0 3 * * 1

D 0 3 * * 0

In cron, Sunday can be represented as 0 or 7 in the weekday field.

How often does */10 * * * * run?

A Every 10 hours

B Every 10 seconds

C Every 10 minutes

D Every 10 days

The */10 in the minute field means every 10 minutes.

What does the * symbol mean in a cron expression?

A Every possible value for that field

B No value

C Only one specific value

D A comment

The asterisk means 'every' possible value for that field.

Which cron expression runs a task at 11:45 PM every day?

A 11 45 * * *

B 23 45 * * *

C 45 11 * * *

D 45 23 * * *

The first field is minutes (45), second is hour (23 = 11 PM).

Describe how to read a cron expression and explain what each field means.

Think of the cron expression as a schedule with five parts: minute, hour, day, month, and weekday.

Explain how to schedule a task to run every weekday at 8 AM using a cron expression.

Remember weekdays are numbers 1 to 5 in cron.