用简单的test语句来判断是否闰年

#! /bin/bash 
read -p "sd " year

if [  $((year%4)) -eq 0 -a  $((year%100)) -ne 0 -o $((year%400)) -eq 0  ]
	then
		echo "是润年"
	else
		echo "不是闰年"
fi

判断一个数是否为偶数

#! /bin/bash 
read -p "sd " a

if   [  $a -ge 2  -a  ((a%2)) -eq 0  ]
then 
	echo  "是偶数"
else 
	echo "不是偶数"
fi

#! /bin/bash 
read -p "sd " a

if   [  $a -ge 2  -a  $((a%2)) -eq 0  ]
then 
	echo  "是偶数"
else 
	echo "不是偶数"
fi
if  [ $a -ge 90 -a $a -le 100  ]
then
	echo  "A "
 elif  [  $a -ge  60  -a  $a -le 89 ]
     then
	 echo  "B"
 elif  [ $a -ge  0  -a $a -le 59 ]
 then
	 echo "C"
 else
	 echo "review"
fi