Running a cron job on Linux every six hours

Question

How can I run command every six hours every day?

I tried the following, but it did not work:

/6 * * * * *  mycommand

Answer 1

You need to use *

0 */6 * * * /path/to/mycommand

Also you can refer to https://crontab.guru/ which will help you in scheduling better...

Answer 2

0 */6 * * * command

This will be the perfect way to say 6 hours a day.

Your command puts in for six minutes!

Answer 3

You should include a path to your command, since cron runs with an extensively cut-down environment. You won't have all the environment variables you have in your interactive shell session.

It's a good idea to specify an absolute path to your script/binary, or define PATH in the crontab itself. To help debug any issues I would also redirect stdout/err to a log file.

Answer 4

You forgot a *, and you've too many fields. It's the hour you need to care about

0 */6 * * * /path/to/mycommand

This means every sixth hour starting from 0, i.e. at hour 0, 6, 12 and 18 which you could write as

0 0,6,12,18 * * * /path/to/mycommand

Answer 5

0 */6 * * *

crontab every 6 hours is a commonly used cron schedule.

Answer 6

Please keep attention at this syntax:

* */6 * * *

This means 60 times (every minute) every 6 hours,

not

one time every 6 hours.