Some variables are blank when using cron to run a script

Question

I'm trying to do a keep alive script to my java process. When they are running they create and update a txt with the unix timestamp. The script should check the files in that folder and reboot the process that weren't updated for more than 10 minutes. When I run the script manually it works fine, but when the cron runs it some variables are blank in the log. I found some similar questions, but they are all about enviroment variables. Here is a piece of my code, with the variables that are blank:

#!/bin/bash
IFS=$'\n'
for file in /home/.../keepAlive/*
do
  value=`cat $file`
  echo "File: ${file#/home/.../keepAlive/}"
  date="$(($(date +%s)*1000))"
  dif=`expr $date - $value`
  dif=`expr $dif / 60000`
  echo "Updated $dif minutes ago"
echo "${file#/home/.../keepAlive/} checked at `date` with $dif minutes" >> /home/.../keepAlive.log
if [ $dif -gt '600000' ]
then
(...)

Anyone know why the variables $value, $date are blank? This is the first time I ask a question here, I'm sorry if I did something wrong. Thank you!

Answer 1

Percent character has a special meaning in crontab, you need to quote it, so change:

date="$(($(date +%s)*1000))"

to

date="$(($(date +\%s)*1000))"