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How to schedule a cron job using shell script?
Schedule cron job via crontab using shell script with examples. Before we start we need to give crontab privilege to the respective user. For the sake of this article I will create some sample cron job for root and deepak user, so I will assign permission for these two users. I will create some dummy jobs.
Where do I find the list of cron jobs?
How to List all Active Cron Jobs Running. To list all scheduled cron jobs for the current user, enter: crontab –l. Cron jobs are typically located in the spool directories. They are stored in tables called crontabs. You can find them in /var/spool/cron/crontabs.
Is there a way to change the cron file?
No, there is no option in crontab to modify the cron files. You have to: take the current cron file (crontab -l > newfile), change it and put the new file in place (crontab newfile). If you are familiar with perl, you can use this module Config::Crontab. It shows the result of your setup in human readable format.
Can a script write a cron tab to a temporary file?
Therefore, a script can either directly write cron tab files, or write them to a temporary file and load them with the crontab [path to temp file] command. Writing directly saves having to write a temporary file, but it also avoids the safety check.
Where do I get the cron error message?
Cron error messages are usually – by default – sent via email. You can check whether there’s email for root with sudo mail, or by just checking contents of /var/mail/root, e.g sudo less /var/mail/root. As Alexis Wilke already said, cron have different mechanism for setting environment variables.
How to add a cron job to crontab?
To add it to the crontab, with no duplication: To remove it from the crontab whatever its current schedule: We also ignore the time scheduling and only look for the command. This way; the schedule can be changed without the risk of adding a new line to the crontab