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By default, cron checks crontabs for cronjobs every minute. If you want to run a job every n seconds you need to use a simple workaround.
Specify multiple jobs with offsets
The easiest way to run a job every n seconds is to run a job every minute and, and sleep in a loop in n second intervals.
Every 5 seconds
script.sh
i=0
while [ $i -lt 12 ]; do # 12 five-second intervals in 1 minute
command/to/run & #run your command
sleep 5
i=$(( i + 1 ))
done
/etc/crontab
* * * * * script.sh
Every 10 seconds
script.sh
i=0
while [ $i -lt 6 ]; do # 6 ten-second intervals in 1 minute
command/to/run & #run your command
sleep 10
i=$(( i + 1 ))
done
/etc/crontab
* * * * * script.sh
Every 15 seconds
script.sh
i=0
while [ $i -lt 4 ]; do # 4 ten-second intervals in 1 minute
command/to/run & #run your command
sleep 15
i=$(( i + 1 ))
done
/etc/crontab
* * * * * script.sh
Every 30 seconds
script.sh
i=0
while [ $i -lt 2 ]; do # 2 ten-second intervals in 1 minute
command/to/run & #run your command
sleep 30
i=$(( i + 1 ))
done
/etc/crontab
* * * * * script.sh
Every 30 seconds (different way)
/etc/crontab
* * * * * script.sh
* * * * * sleep 30 ; script.sh
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How to get cron job errors in email with MAILTO?
One of the neat features of Cron is the ability to send emails when an error occurs during the execution of the cronjob. This can be done using the `MAILTO` environmental variable. When executing cronjob, any output is mailed to the owner of the crontab or to the user or email address specified in the `MAILTO` environment variable in the crontab, if such exists.
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How to view and read cron logs on Ubuntu, Debian and CentOS?
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