Write a shell script that accepts one or more file names as arguments, and converts them all to upper case if they exist

for var in $@
do
check=`ls -al $var 2>/tmp/err | grep -w $var | cut -d " " -f 9`
if [ "$check" == "$var" ];then
upper_case=`echo $var | tr '[a-z]' '[A-Z]'`
echo "file before uppercase"
echo $var
echo "***file after uppercase***"
mv $var $upper_case
echo $var
else
echo "$var file doesnt exists"
fi
done