shell 随机数组

cat  txt

211.138.124.179:80
221.130.17.61:80
219.135.215.37:8080
202.101.124.18:80
221.130.18.53:80
221.130.18.124:80
221.130.23.125:80
202.108.5.153:80
218.25.99.135:808
218.25.106.219:80
218.93.205.150:808

#!/bin/bash
i=1
for  line in  `cat txt2`
  do
     arg[i]="$line"
     i=$i+1
  done
echo  ${arg[$RANDOM % ${#arg[*]}+1]}