I have the following cron job command running once daily on my NAS device:
find /nfs/rpiggott/complete -mtime +45 -exec rm {} \;
I am wondering if there is a way to pipe a list that will result in the cron sending an e-mail to me showing what file it delete and / or any errors experienced.
For this purposes you system should be able to send emails. So you could install and configure postfix:
sudo apt install postfix
For General type of mail configuration choose Internet Site, if you want to do more detailed configuration use the command:
sudo dpkg-reconfigure postfix
At this stage Cron will start to send emails. Everything that usually will be outputted to the STDOUT (if you are execute a command in the command line), including all error messages, will be sent to the local mailbox of the user that runs the Cronjob.
The default location of local user's mail boxes is /var/mail/. You can install the command-line email client mutt to read your user's email box via the command line in a convenient way:
sudo apt install mutt
mutt installation process will involve installation and configuration of postfix if it isn't done before.You can change the default destination mailbox by changing the value of the envvar MAILTO within crontab, before the definition of the Cronjob.
Please note: unless you haven't enabled SSL/TLS certificate within you send mail configuration, most of the public mail servers will ignore your emails in some way. For example mail.google.com will put them into the spam. If this is a server instance and you already have SSL/TLS certificate for your primary domain follow this nice manual to attach it to Postfix.
Once your system is able to send emails you must make your Cronjob more verbose (for e.g. add -v to the rm command) and must set proper value of MAILTO. So your crontab should look as this:
MAILTO="example.email@gmail.com"
* * * * * find /nfs/rpiggott/complete -mtime +45 -exec rm -v {} \;
Another approach is to create a script (which will be executed via crontab) that includes your command and uses mail, mutt, ssmtp or sendmail to send emails. See the bottom of the references for mor details.
References and further reading:
I used a pretty simple method to get cron to send emails: Backup Linux configuration, scripts and documents to Gmail.
From Send email alerts using ssmtp we find the simplest way of sending email automated from terminal or script. The installation steps are straight forward:
sudo apt install ssmtp
sudo nano /etc/ssmtp/ssmtp.conf
# Change "MyEmailAddress" and "MyPassword" to your own.
There is one step not mentioned; Google will send you an email confirming you want to allow a "less secure" application to send mail with your account:
There is an annoyance of getting too much mail. For example every time you mistype your sudo password you will get an email: Stop emailing me bad sudo password attempts
Allow less secure apps you could instead Create an App Password and use that password in ssmtp instead of your own: Google will accept the email, not send to Spam, and as an added bonus you get the benefit of not keeping your real gmail password in your PC
– MestreLion
Apr 01 '21 at 22:06
findalso recognize the+sign instead of\;, i.e.find … -exec rm -v {} +(instead offind … -exec rm -v {} \;. Depending on the number of files this will greatly improve performance: with\;thermcommand is run once per file (i.e. 1000 times for 1000 files) whereas the+variant will runrmwith as many filenames as parameter as fit into the command line (i.e. it will callrmonly twice or so, once with 800 files and a second time with 200 files). – PerlDuck Apr 01 '18 at 16:19rm [800 filenames]: failedwhereas the\;would help to better identify the error because just a single filename is given. – PerlDuck Apr 01 '18 at 16:22\;or+is engaged while-exec rm -v {}is used, the output is identical so probably+is a better choice. @PerlDuck – pa4080 Apr 01 '18 at 16:27