求解整数表达式预期错误

Question

编写此代码会给我一个IF行上预期的整数表达式 我怎么能解决这个问题？！

uservalue=$1

df -h | tail -n +2 > dfout.txt

cat dfout.txt | while read Filesystem Size Used Avail Use Mounted

do 

use_perc="{Use%?}"

if [ "use_perc" -gt "$uservalue"]

then

echo "$Filesystem is full"

else

echo "$Filesystem is not full"

fi

done