cron & crontab

Question 1

How to check crontab for all users on server?

Answer 1

?

Question 2

How to edit your own crontab?

Answer 2

crontab -e

Question 3

Edit root crontab?

Answer 3

sudo crontab -e

Question 4

Crontab sections?

Answer 4

minute (0-59), hour (0-23, 0 = midnight), day (1-31), month (1-12), weekday (0-6, 0 = Sunday), command
like in ‘01 04 1 1 1 /usr/bin/somedirectory/somecommand’ (which will run at 4:01am on January 1st plus every Monday in January)

Question 5

What is asterisk symbol meaning in crontab?

Answer 5

Every instance of given time period will be used. Say, first * means that a script will run every minute, etc.

Question 6

What are comma-separated values in crontab sections?

Answer 6

Означают, что событие должно происходить несколько раз за определенный период времени. Например, 01,31 в минутах означает, что команда будет запускаться в 1 и 31 минуту (указанного дальше периода времени)

Question 7

What are divisors (/) in crontab sections?

Answer 7

Run a script some number of times per time unit. For example if you want to run it every 10 minutes use the following crontab entry (runs on minutes divisible by 10: 0, 10, 20, 30, etc.): */10 etc.
(equiv. to 0,10,20,30,40,50 etc.)

Question 8

What option is to show current crontab to stdout?

Answer 8

crontab -l

Question 9

What option removes current crontab?

Answer 9

crontab -r

Question 10

What editor will be used when editing current crontab via crontab -e?

Answer 10

Specified in $EDITOR env var.