linux grep在shell脚本里面的循环问题

#!/usr/bin/env bash

echo "$0 $@" #print the command line for logging
set -e
logdir="./log"

if [ -d ${logdir} ]
then
echo "traverse the dir :"${logdir}
else
echo ${logdir}" is not a dir "
exit
fi

while true
do
    for i in `ls ${logdir}`;
do
echo "#####the ${i} th process log :#####"
echo ${i}
cat ${logdir}/${i} | grep -iv "ERROR"
# awk '/ERROR/' ${logdir}/${i}

done
sleep 30
done

循环里面 grep 会退出循环

awk 则不会