Linux -Shell 编程学习（二）

*case多选结构：
基本结构

case word in 
	case-1)
	command-1
	;;
	case-2)
	command-2
	;;
	case-3)
	command-3
	;;
	......
	case-n)
	command-n
	;;
esac

一个Demo

#! /bin/bash
case "$1" in
        start)
                echo -n "Starting SSH daemon"
                ;;
        stop)
                echo -n "Shutting down SSH daemon"
                ;;
        restart)
                echo -n "Restart SSH daemon"
                ;;
esac

*while 循环

while test-commands
do
	command-self
done

Demo
一个求1+2+3+…+100的例子

#! /bin/bash
sum=0
number=1
while [ $number -le 100 ]
do
        sum=$[$sum+$number]  #sum = sum + number
        let number=$number+1 #number++
done

echo "The summary is equal $sum"

一个求1+2+…+n的Demo

#! /bin/bash
echo "Please input a number greater Than zero Or Exit."
while read n
do
        sum=0
        count=1
        if [ $n -gt 0 ]
        then
                while [ $count -le $n ]
                do
                        sum=$[$sum+$count]
                        let count=$count+1
                done
                echo "The summary is $sum."
        else
                exit
        fi
        echo "Please input a number greater than zero Or Exit."
done

*for语句

for variable in list
do
	command-self
done

shell里面的for与Python的很像.

for i in range(1,101):
	print(i)

上面这个python代码在Shell里面

#! /bin/bash
for i in `seq 1 100`
do
	echo "$i"
done