my_script.sh

#!/bin/bash

mkdir -p trash
LOG=trash/$$_my_script.log
echo "Started" >> $LOG

echo "Find my log file investigating my source ;)"

sleep 120

# tip: -neq means "not equal to"
which apt-get
if [ $? -eq 0 ]; then
        sudo apt-get install dstat >> $LOG
else
        echo "not a debian based distro" >> $LOG
fi

# tip: -eq means "equal to"
which yum
if [ $? -eq 0 ]; then
        sudo yum install -y dstat && echo "dstat installed" >> $LOG
else
        echo "ERROR. Check log file" >> $LOG
fi

exit 0