Shell--- circular statement practice

1. Use case Realize the judgment of good and bad grades ：

read -p "your score:" score
case "$score" in
  [0-5][0-9])
    echo "failure"
    ;;
  [6-7][0-9])
    echo "normal"
    ;;
  [8-9][0-9]|100)
    echo "excellent"
    ;;
  *)
    echo "please input right score!"
    ;;
esac

Execution results ：

[[email protected] ~]# chmod +x ca.sh 
[[email protected] ~]# ./ca.sh 
your score:34
failure
[[email protected] ~]# ./ca.sh 
your score:98
excellent
[[email protected] ~]# ./ca.sh 
your score:67
normal

2. for establish 20 Users （ Let me first create two examples ）, The user prefix is entered by the user , The user's initial password is entered by the user , for example test01,test10;

read -p "Please input your usernames:" username
[ -z "$username" ] && echo "you must input the usernames!" && exit 1

read -p "Please input your passwd:" passwd
[ -z $passwd ] && echo the passwd could not be null! && exit 2
for i in `seq 2`
do
  id $username$i &> /dev/null
  if [ $? -eq 0 ];then
    echo "the user is already exist"
  else
    useradd $username$i &>/dev/null
    echo $passwd | passwd --stdin $username$i >/dev/null
    id $username$i &> /dev/null
    if [ $? -eq 0 ];then
      echo $username$i is ok
    else
      echo $username$i is not ok
    fi
  fi
done

The results are shown below ：

[[email protected] ~]# chmod +x cu.sh
[[email protected] ~]# ./cu.sh 
Please input your usernames:test
Please input your passwd:123456
test1 is ok
test2 is ok

3.for ping Test refers to the host of the network segment , The network segment is input by the user , For example, user input 192.168.2 , be ping 192.168.2.10 --- 192.168.2.20

        UP： /tmp/host_up.txt

        Down: /tmp/host_down.txt

read -p "Please enter the network:" IP
for i in `seq 10 20`
do
  ping -c2 $IP.$i &> /dev/null
  if [ $? -eq 0 ];then
    echo $IP.$i is UP >> /tmp/host_up.txt
  else
    echo $IP.$i is DOWN >> /tmp/host_down.txt
  fi
done

The results are shown below ： Need to go /tmp/host-down File View output information ;

[[email protected] ~]# cat /tmp/host_down.txt 
192.168.188.10 is DOWN
192.168.188.11 is DOWN
192.168.188.12 is DOWN
192.168.188.13 is DOWN
192.168.188.14 is DOWN
192.168.188.15 is DOWN
192.168.188.16 is DOWN
192.168.188.17 is DOWN
192.168.188.18 is DOWN
192.168.188.19 is DOWN
192.168.188.20 is DOWN

4. Use for Realize batch host root Password modification , Success or failure must be recorded ; Tips ： host IP In a file ,SSH： Implement public key authentication , Execute host commands in remote , Implement public key authentication

# ssh-keygen Generate a key pair on the master for management

# ssh-copy-id -i 192.168.2.3