shell脚本，检查给出的字符串是否为回文

[root@localhost wyb]# cat .sh
#!/bin/bash
#检查给出的字符串是否为回文
 
read -p "Please input a String:" number
[ -z $number ] && echo "input nothing " && exit 
 
len=${#number}
count=$((len/))
 
for i in `seq $count`
do
      lasti=$((len-i+))
      first=`echo $number|cut -c $i`
      two=`echo $number|cut -c $lasti`
 
     [[ "$first" !=  "$two"  ]] && echo no && exit 
 
done
echo yes
[root@localhost wyb]# bash .sh
Please input a String:
yes
[root@localhost wyb]# bash .sh
Please input a String:
yes
[root@localhost wyb]# bash .sh
Please input a String:
no
[root@localhost wyb]# bash .sh
Please input a String:
yes
[root@localhost wyb]# 

用rev来检查是不是回文
[root@localhost wyb]# cat rev12321.sh
#!/bin/bash
#检查给出的字符串是否为回文
read -p "Please input a String:" number
[ -z $number ] && echo "input nothing " && exit 
 
a1=`echo $number|tac`
b2=`echo $number|rev`
[[ "$a1" != "$b2" ]] && echo no || echo yes
 
[root@localhost wyb]# bash rev12321.sh
Please input a String:
no
[root@localhost wyb]# bash rev12321.sh
Please input a String:
yes
[root@localhost wyb]# bash rev12321.sh
Please input a String:
no
[root@localhost wyb]# bash rev12321.sh
Please input a String:
yes
[root@localhost wyb]# 

[root@localhost wyb]# cat rev.sh
#!/bin/bash
#检查给出的字符串是否为回文
 
read -p "Please input a String:" number
[ -z $number ] && echo "input nothing " && exit 
 
number2=`echo $number|rev`
 
[[  "$number2"  =  "$number" ]] && echo yes  || echo no
[root@localhost wyb]# bash rev.sh
Please input a String:
yes
[root@localhost wyb]# bash rev.sh
Please input a String:
no
[root@localhost wyb]# bash rev.sh
Please input a String:
yes
[root@localhost wyb]#