shell多线程

a='a1'
b='b1'
c='c1'
d='d1'
e='e1'
ARR=($a $b $c $d $e)
rd=`date +%N`
for i in ${ARR[*]}
do
{
sleep 1;echo 1>>aa && echo "done!""${i}""$RANDOM"
}&
done
wait