[: -gt: unary operator expected错误

#!/bin/sh

. /etc/path.conf

file=$1

DEBUGFILE='/tmp/imdebug'
echo $file > ${DEBUGFILE}

if [ ! -e "$file" ]; then
    echo "$file didn't exists."
    exit 1
fi

echo "lalala" >> ${DEBUGFILE}

COUNT=1000
while [ $COUNT -gt 1 ]
do
        echo "COUNT: $COUNT" >> ${DEBUGFILE}
        sh do.sh $file >> ${DEBUGFILE}
        COUNT=`expr $COUNT - 1`
done


原来是COUNT=`expr $COUNT - 1`写成了COUNT=`expr $COUNT-1`，减号前后要有空格，要不然就把它当成一个字符串了。