Linux下生产随机字符

#!/bin/sh 
 
alphabeta="a b c d e f g h i j k l m n o p q r s t u v w x y z" 
number="0 1 2 3 4 5 6 7 8 9" 
 
A=($alphabeta) # save as array 
N=($number) 
num_a=${#A[*]} 
num_n=${#N[*]} 
 
echo ${A[$((RANDOM%num_a))]}${N[$((RANDOM%num_n))]}