list all cron jobs of all users on system

findcrons.sh

#!/bin/sh

# first, find out if we're sudo
if [ $(id -u) -ne 0 ]; then
  echo "Nope. Simon didn't say so.";
  exit 1;
fi

for user in $(cut -f1 -d: /etc/passwd); do
  crons=$(crontab -u $user -l 2>/dev/null | grep -v '^#')
  if [ 0 = $? ]; then
    echo "$user"
    echo "$crons"
  fi
done