Ubuntu – Script not running in crontab, file not found

cron runs jobs in its own minimal environment and doesn't itself read any of the shell startup files such as those in /etc/profile.d/ - by default it's just something like

LANGUAGE=en_CA:en
HOME=/home/steeldriver
LOGNAME=steeldriver
PATH=/usr/bin:/bin
LANG=en_CA.UTF-8
SHELL=/bin/sh
PWD=/home/steeldriver

You have a couple of options:

1. set the variables in a script, and run that from cron. In the case of shell scripts, that's easy (just export them at the top of the script - or source an environment file if you prefer). For Python scripts you may find it easiest to wrap the python call inside a shell script where you can set up the environment first.

2. define the environment as a sequence of name = value pairs inside the crontab like

   ORACLE_HOME = /usr/lib/oracle/12.2/client64
   * 5 * * * /path/to/some/executable
   

   (spaces are allowed around the = since it's not a script); however note that this method does not expand variables so you can't do stuff like PATH=$PATH:/whatever

See man 5 crontab for details.

You're missing a space after the command bash and the argument -c.

This should work:

0 15    * * *  root bash -c 'for i in /home/dell/Downloads/*.{pdf,docx,png,jpg,PDF,DOCX}; do shred -zvu "$i" -n20; done'

Some additional hints:

• Don't run a crontab as user root if you don't need to.
• You wrote that you put it in /etc/crontab file. Don't edit crontab files directly, rather use crontab -e command or sudo crontab -e for commands which need root rights. Note, that you don't put the user field in the "other" crontab files.

• If you have more than one command you can use bash -c as you do, but I'd rather put the commands in a script and execute this from crontab.

• To run a script on startup, you can use @reboot instead of 0 15 * * *.