cron script not executing on Raspberry Pi

Question

I am not a linux expert and I have a problem I do not manage to solve. I am sorry if it is obvious. I am trying to execute a bash script in a cron table on a raspberry pi, and I don't manage to get it work. Here is the example script I want to execute:

#!/bin/bash

PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/local/games:/usr/games

plouf=$( ps -aux | grep reviews | wc -l)
if [[ "$plouf" == 1 ]] ;
then
    echo "plouf" >> /home/pi/Documents/french_pain/crontest.txt
fi

My script in the cron consist in starting a script if there is no progam with review in its name running. To test I am just appending "plouf" to a file. I count the number of line of ps -aux | grep reviews | wc -l ps -aux | grep reviews | wc -l ps -aux | grep reviews | wc -l , and if there in only one line I do append "plouf" in a file. Here is my crontab:

crontab -l


SHELL=/bin/bash
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/local/games:/usr/games
* * * * * sudo /home/pi/Documents/french_pain/script2.sh

The script do work when I do ./ script2.sh or /home/pi/Documents/french_pain/script2.sh directly in terminl: it add a "plouf" to the file.

I came across this page and tried different possibilities, by setting my path as the path given by env , and by explicitly setting the shell in the cron. But still not working. What I am I doing wrong?

---

To answer Mark Setchell comment:

raspberrypi:~/Documents/french_pain $ sudo /home/pi/Documents/french_pain/script2.sh
raspberrypi:~/Documents/french_pain $ cat crontest.txt
plouf

and cron is running:

raspberrypi:~/Documents/french_pain $ pgrep cron
353

I manage to do simple jobs like

* * * * * /bin/echo "cron works" >> /tmp/file

I tried with the direct path to the commands:

plouf=$( /bin/ps -aux | /bin/grep 'R CMD.*reviews' | usr/bin/wc -l)
if [[ "$plouf" == 1 ]] ;
then
   /bin/echo "plouf" >> /home/pi/Documents/french_pain/crontest.txt
fi

without any luck. The permission for the file:

-rw-rw-rw- 1 root root 6 juil. 3 23:30 crontest.txt

I tried deleting it, and did not work either. help !

Answer 1

I guess you trying this as "pi" user then 'sudo' won't work unless you have allowed nopasswd:all or using a command that is able to handle the password that Sudo requires from stdin in this case. The example below is dangerous since it will not require any password for sudo command anymore but since you wanted to use sudo in cronie:

Example 1:

With default /etc/sudoers below example will create an empty file:

* * * * * sudo ls / > ~/cronietest.txt 

Try add below in /etc/sudoers at bottom (obs: do not use pi as username on a rpi):

pi ALL=(ALL) NOPASSWD:ALL

Now try again to add below in crontab

* * * * * sudo ls / > ~/cronietest.txt 

It works!

Example 2:

This is more safe, add this to sudoers file for allow 'command' for "pi" user without any password when sudo is executed:

pi ALL= NOPASSWD: /bin/<command>

Example 3:

Without editing sudoers file, this is another example that will work (this is dangerous since your password is stored in cron file as plaintext)

* * * * * echo "password" | sudo -S ls / > ~/cronietest.txt

Answer 2

I did not find the reason why the sript was not working, but I finally found a way to make it work thanks to this post : I used shell script instead of bash: The file script3.sh

#!/bin/sh

if ps -ef | grep -v grep | grep 'reviews'; then
      exit 0
else
      echo "plouf" >> /home/pi/Documents/french_pain/crontest.txt
fi

together with

* * * * * /home/pi/Documents/french_pain/script3.sh

in my crontab did the work I wanted.