Crontab examples Linux

Important Crontab Examples

1. What is the use of * * * * * in cron?
2. What is an example of a cron job?
3. What does 30 * * * * mean in crontab?
4. What does * 5 * * * mean in cron?
5. What do * mean in crontab?
6. Does cron have 6 or 7 fields?
7. Does cron have 5 or 6 fields?
8. How do I schedule a cron job every 5 minutes?
9. How do I run a cron job every 20 minutes?
10. What does 0 * * * * mean in crontab?
11. How do I schedule a .sh file in Linux?

What is the use of * * * * * in cron?

What Is the Use of * * * * * In Cron? * * * * * is a cron schedule expression wildcard, meaning your cron job should run every minute of every hour of every day of every month, each day of the week.

What is an example of a cron job?

Cron Job every weekday during working hours

This example checks the status of the database every weekday (i.e excluding Sat and Sun) during the working hours 9 a.m – 6 p.m.

What does 30 * * * * mean in crontab?

*/30 * * * * your_command. this means "run when the minute of each hour is evenly divisible by 30" (would run at: 1:30, 2:00, 2:30, 3:00, etc) example #3. 0,30 * * * * your_command. this means "run when the minute of each hour is 0 or 30" (would run at: 1:30, 2:00, 2:30, 3:00, etc)

What does * 5 * * * mean in cron?

Show activity on this post. 5 * * * * means it runs once per hour at five minutes past the hour. */5 * * * * means it runs once every five minutes.

What do * mean in crontab?

* = always. It is a wildcard for every part of the cron schedule expression. So * * * * * means every minute of every hour of every day of every month and every day of the week .

Does cron have 6 or 7 fields?

A cron expression is a string consisting of six or seven subexpressions (fields) that describe individual details of the schedule. These fields, separated by white space, can contain any of the allowed values with various combinations of the allowed characters for that field.

Does cron have 5 or 6 fields?

The CRON expressions consists of 6 fields, separated by space: e.g. 0 0/15 * * * * , which describes time points every 15 minutes starting from minute 0.

How do I schedule a cron job every 5 minutes?

A crontab has 5 fields separated by spaces. Each of the fields specifies the date and time a command should execute. To execute a crontab every 5 minutes, we need to use the slash (/) special character followed by 5, which acts as a step that crontab should execute the command after every 5 minutes.

How do I run a cron job every 20 minutes?

For example, if you have 1-10/2 in the Minutes field, it means the action will be performed every two minutes in range 1-10, same as specifying 1,3,5,7,9 . Instead of a range of values, you can also use the asterisk operator. To specify a job to be run every 20 minutes, you can use “*/20”.

What does 0 * * * * mean in crontab?

0 * * * * -this means the cron will run always when the minutes are 0 (so hourly) 0 1 * * * - this means the cron will run always at 1 o'clock. * 1 * * * - this means the cron will run each minute when the hour is 1. So 1:00 , 1:01 , ... 1:59 .

How do I schedule a .sh file in Linux?

Here, by using an asterisk in the last three fields (1-31 days, 1-12 months, all days of the week), our backups.sh script will run every day at 3 pm. In the above expression, 2-50/10 in the minute field indicates the second minute of the hour and every 10 minutes thereafter.