SHELL“多线程”编程(请教)

#!/bin/sh
file=/etc/list
eno=0;
rno=0;
sum=0;
if [ "$2" == "" ];then
    num=100
else
    num=$2
fi
while read line
do
    if [ "$num" -eq "$sum" ];then
        break
    fi
#   sum=$(expr $sum + 1)
    ip[$sum]=`echo $line | sed -n 's/^.*(\(.[0-9\.]*\)).*$/\1/p'`
    addr[$sum]=`echo $line | sed -n 's/^\(.*\)(.*/\1/p'`
    result[$sum]=`nslookup $1 ${ip[$sum]} | grep Address | sed -n '2,$p' | cut -d: -f2`
    sum=$(expr $sum + 1)
    #echo ${ip[$sum]}
    #echo ${result[$sum]}
    echo -n "."
done < $file
echo
for line in `seq 1 $sum`
do
    t=$(expr $line - 1)
    if [ "${result[$line]}" = "" ];then
#      result=" Error!!"
       echo -n " "$line"=>"
       echo -en "\033[32m ${addr[$t]} \033[0m:"
       echo -e "\033[37m "Error"($1) \033[0m"
       eno=$( expr $eno + 1 )
    else
       echo -n " "$line"=>"
       echo -en "\033[32m ${addr[$t]} \033[0m:"
       echo -e "\033[31m ${result[$t]}($1) \033[0m"
       rno=$( expr $rno + 1 )
    fi
done
echo "========================================"
echo -n "eno="$eno";rno="$rno";"
echo -n "Error=" `echo $eno $sum | awk '{print $1 / $2 * 100 "%;";}'`
echo "Success=" `echo $rno $sum | awk '{print $1 / $2 * 100 "%;";}'`
echo "========================================"
#file文件内容格式如下：
广西南宁市铁通(222.52.118.162)广西南宁市铁通(222.52.118.163)河南省电信(222.85.85.85)河南省洛阳市电信(222.88.88.88)云南省电信(222.172.200.68)湖南省电信(222.243.129.81)

其中红色这句执行很非常的慢，循环起来非常耗时，想有什么好的方法来解决这个问题，但又不影响功能,如果你看到了，还请指教。