Common cron expressions in Linux CLI - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of this cron expression schedule?

Given the cron expression 0 0 * * 0, what does it schedule?

A Runs the job every Sunday at midnight

B Runs the job every day at midnight

C Runs the job every hour on Sundays

D Runs the job every Sunday at noon

💡 Hint

Remember the fields: minute, hour, day of month, month, day of week.

The cron expression '0 0 * * 0' means minute 0, hour 0 (midnight), every day of month, every month, and day 0 which is Sunday in cron. So it runs every Sunday at midnight.

💻 Command Output

intermediate

What does this cron expression do?

What is the schedule for the cron expression */15 9-17 * * 1-5?

A Runs every 15 minutes from 9 AM to 5 PM on weekends

B Runs every 15 minutes all day on weekdays

C Runs every 15 minutes from 9 AM to 5 PM, Monday to Friday

D Runs every 15 minutes from 9 AM to 5 PM every day

💡 Hint

Look at the hour and day of week fields carefully.

The expression '*/15' in minutes means every 15 minutes. '9-17' in hours means from 9 AM to 5 PM. '1-5' in day of week means Monday to Friday. So it runs every 15 minutes during working hours on weekdays.

💻 Command Output

advanced

What is the output of this cron expression?

What schedule does the cron expression 30 23 1 * * represent?

A Runs at 11:30 PM on the first day of every month

B Runs at 11:30 AM on the first day of every month

C Runs at 11:30 PM every day

D Runs at 11:30 PM on the first Monday of every month

💡 Hint

Check the day of month and hour fields.

The expression means minute 30, hour 23 (11 PM), day 1 of the month, every month, every day of week. So it runs once a month at 11:30 PM on the first day.

💻 Command Output

advanced

What error or output does this cron expression produce?

What happens if you use the cron expression 60 24 * * *?

A Runs at midnight every day

B Runs at 24:00 every day (valid time)

C Runs at 00:00 on the 60th day of the month

D It causes an error because 60 is invalid for minutes

💡 Hint

Minutes range from 0 to 59, hours from 0 to 23.

Minute field cannot be 60 (valid range 0-59). Hour field cannot be 24 (valid range 0-23). So this expression is invalid and causes an error.

🧠 Conceptual

expert

How many times does this cron expression run in a week?

How many times will the job run with the cron expression 0 12 */2 * 1 in one week?

A 4 times

B 3 times

C 1 time

D 0 times

💡 Hint

Cron uses OR logic for day of month and day of week fields interaction.

In standard Linux cron, the job runs when either the day-of-month OR day-of-week matches (minute, hour, month also match). '*/2' matches even days of month (2,4,6,...30), '1' matches Monday. It runs at 12:00 on even days of the month OR Mondays. A week typically has 3 even days, so 3 times.