=========================DEMO1==========================

#！/bin/bash
read -p "Please input your number:" num
read -p "Please input your password:" -t 5 passwd
echo 账号: $num  密码: $passwd

=========================DEMO2==========================

#!/bin/bash
echo -n "\$0:  "
echo "Program name is $0"
echo -n "\$#:  "
echo "There are totally $# parameters"
echo -n "\$*:  "
echo "The parameters is: $*"
echo -n "\$\$:  "
echo "The program's pid is $$"
echo -n "\$?:  "
echo "The program result is $?"

=========================DEMO3==========================


#!/bin/bash
function login(){
    echo -n "Login : "
    read name
    stty -echo    ###### doesn't show what you input
    echo -n "Password : "
    read passwd
    stty echo
    errcount=$((errcount+1))
    judge
}
function judge(){
##if [ $name = "zhang" -a $passwd = "618" ];then
tmpnp=$name$passwd
awk '{print $1$2}' /zhang/shell/testfile/users | grep $tmpnp
if [ $? = 0 ];then
    echo "Login success!"
    elif [ $errcount -eq 3 ] ;then
        echo "You have tried 3 times!"
        exit
    else
        /usr/bin/clear
        echo "Your have `expr 3 - $errcount` times changes!"
        login
fi
}
errcount=0
login

=========================DEMO4==========================

#!/bin/bash
### FUNCTION ： case
echo  -n 'Enter [Y|N]:'
read tmp
case $tmp in
    y|yes|Y|YES) echo "You enter is $tmp"
    ;;
    n|no|N|NO) echo "You enter is $tmp"
    ;;
    *) echo "erro"
    ;;
esac

=========================DEMO5==========================

#!/bin/bash
factorial=1
for num in `seq 1 10`
do
    factorial=`expr $factorial \* $num`
done
echo "10! = $factorial"

=========================DEMO6==========================

#! /bin/sh
while true
do
   echo "*******************************"
   echo "Please select your operation:"
   echo " 1 Copy"
   echo " 2 Delete"
   echo " 3 Backup"
   echo " 4 Quit"
   echo "*******************************"
   read op
   case $op in
        C|c)
          echo "your selection is Copy"
           ;;
        D|d)
          echo "your selection is Delete"
          ;;
        B|b)
         echo "your selection is Backup"
           ;;
        Q|q)
          echo "Exit ..."
               break
          ;;
        *)
          echo "invalid selection,please try again"
   esac
done