if嵌套语句 shell脚本实例 测试是否闰年

在 if 语句里面，你可以使用另外一个 if 语句。只要你能逻辑管理

你就可以使用多层嵌套。 以下是一个测试闰年的例子：

#!/bin/bash

# This script will test if we're in a leap year or not.

year=`date +%Y`

if [ $[$year % 400] -eq "0" ]; then  

   echo "This is a leap year.  February has 29 days."

elif [ $[$year % 4] -eq 0 ]; then        

       if [ $[$year % 100] -ne 0 ]; then          

          echo "This is a leap year, February has 29 days."        

       else          

          echo "This is not a leap year.  February has 28 days."        

       fi

else   echo "This is not a leap year.  February has 28 days."

fi

# echo `date +%Y` 2009

# ./leapyear.sh This is not a leap year.  February has 28 days.

--------------------------------------------------------------------

以上的脚本可以用布尔操作符 “AND(&&)” 和 “OR(||)” 来缩短

#!/bin/bash

# This script will test if we're in a leap year or not.

year=`date +%Y`

if (( ("$year" % 400) == "0" )) || ((("$year" % 4 == "0") && ("$year" % 100 != "0") )); then  

      echo "This is a leap year." else   echo "This is not a leap year."

fi

# ./leapyear2.sh This is not a leap year.

--------------------------------------------------------------------------

同样可以使用内建命令read来捕捉用户的输入，来测试是否为闰年：

#!/bin/bash

# This script will test if you have given a leap year or not.

echo "Type the year that you want to check (4 digits), followed by [ENTER]:"

read year

if (( ("$year" % 400) == "0" )) || (( ("$year" % 4 == "0") && ("$year" % 100 != "0") )); then  

   echo "$year is a leap year."

else  

   echo "This is not a leap year."

fi

# ./leap2.sh

Type the year that you want to check (4 digits), followed by [ENTER]: 2009 This is not a leap year.