Tips and Tricks

Install, Edit, or Remove Cron Jobs

1. Install Crontab in Batch Mode

By specifying the file name as an argument to crontab command, you can install the new cron jobs from a text file as shown below.

First create a text file with all your cron job entries.

$ cat cron-file.txt
* * * * * /bin/date >> /tmp/date-out
* * * * * /bin/ls >> /tmp/ls-out

Next, install the cron jobs from a text file as shown below.

$ crontab cron-file.txt

Note: This will overwrite the existing cron entries.

2. Edit crontab in Batch Mode

You can edit the crontab in batch mode using various methods (for example, using sed).

Example: Change output redirection from write to append for all cron jobs.

$ crontab -l
* * * * * /bin/date > /tmp/date-out
* * * * * /bin/ls > /tmp/ls-out

$ crontab -l | sed 's/>/>>/' | crontab -

$ crontab -l
* * * * * /bin/date >> /tmp/date-out
* * * * * /bin/ls >> /tmp/ls-out

3. Remove All cron jobs of the Current User

Crontab’s -r option removes all cron job for the current user. If you have appropriate privilege, you can even remove other user’s cron jobs using the -r option along with the -u user option.

Example: Remove the current user cron entries.

$ crontab -r

Example: Remove the specified user cron entries.

$ crontab -r -u USERNAME

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