shell---case、for、while

#!/bin/bash                                //程序开始
#File: case.shecho "=========="
echo "Welcome!"echo "1 Copy"
echo "2 Delete"
echo "3 Backup"
echo "4 Quit"
echo "=========="
echo "Please input your select:"
read n               //读取输入内容
case $n in
1)  echo "Your select is Copy!"    ;;
2)  echo "Your select is Delete!"   ;;
3)  echo "Your select is Backup!"   ;;
4)  echo "Your select is Quit!"    ;;
*)  echo "Your select is invalid!"  ;;
esac                                       //程序结束

#!/bin/bash        //程序开始
#File: for.sh
for n in 1 2 3 4 5       //将n依次循环赋值
do
echo "The number is : $n"
done               //程序结束

#!/bin/bash                  //程序开始
#File: while.sh

n=1
while [ $n -lt 10 ]       //只要n小于10就执行
do
squ=`expr $n \* $n`      //将n做平方
echo $squ                    //输出平方值
n=`expr $n + 1`        //n逐步加1，以匹配10
done                          //程序结束

#!/bin/bash                   //程序开始
#File: var.sh
n=1
while [ "$n" -lt "100" ]
do
echo "The value is : $n"
n=`expr $n \* 2`
done                          //程序结束

#!/bin/bash                   //程序开始
#File: interactive.sh
read -p "Please input a number:" num        //读入输入的行数
read -p "Please input a charsymbol:" sym    //读入显示的符号
a=1
while [ $a -le $num ]          //外层循环，a小于等于输入的行数
do
b=1                       //b代表打印的符号的个数
while [ $b -le $a ]            //打印的符号个数小于等于行数
do
echo -n "$sym"       //-n表示不换行，打印符号
b=`expr $b + 1`    //符号数不断的增加，以匹配a
done
echo             //表示换行
a=`expr $a + 1`         //a不断的增加，以匹配行数
done                          //程序结束