Shell exercises

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

[[email protected] test]# vim score.sh
#!/bin/bash
read -p "please enter your score (0-100):" grade
case "$grade" in
  8[0-9]|9[0-9]|100)
    echo " optimal "
  ;;
  6[0-9]|7[0-9])
    echo " good "
  ;;
   *)
    echo " Bad "
esac
​
[[email protected] test]# chmod a+x score.sh
[[email protected] test]# ./score.sh
please enter your score (0-100):99
 optimal 
[[email protected] test]# ./score.sh
please enter your score (0-100):10
 Bad 
[[email protected] test]# ./score.sh
please enter your score (0-100):67
 good 

2.for establish 20 user

The user prefix is entered by the user

The user's initial password is entered by the user

for example ：test01,test10

[[email protected] test]# vim user20.sh
#!/bin/bash
​
read -p " Enter user prefix :" u
read -p " Enter the user's initial password :" n
for i in {1..20}
do
    useradd $u$i
    echo "$u$i"
    echo "$u$i:$n" | chpasswd
    echo "Initial password changed successfully."
done
[[email protected] test]# chmod a+x user20.sh
[[email protected] test]# ./user20.sh
 Enter user prefix :user
 Enter the user's initial password :123
user1
Initial password changed successfully.
user2
Initial password changed successfully.
user3
Initial password changed successfully.
user4
Initial password changed successfully.
user5
Initial password changed successfully.
user6
Initial password changed successfully.
user7
Initial password changed successfully.
user8
Initial password changed successfully.
user9
Initial password changed successfully.
user10
Initial password changed successfully.
user11
Initial password changed successfully.
user12
Initial password changed successfully.
user13
Initial password changed successfully.
user14
Initial password changed successfully.
user15
Initial password changed successfully.
user16
Initial password changed successfully.
user17
Initial password changed successfully.
user18
Initial password changed successfully.
user19
Initial password changed successfully.
user20
Initial password changed successfully.

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

[[email protected] test]# vim 10.sh
#!/bin/bash
read -p " Please enter a network segment :" n
for i in  {130..140}
do
  if ping -c 3 $n.$i &> /dev/null    
then
    echo "$n.$i is up" >> /tmp/host_up.txt
  else
    echo "$n.$i is down" >> /tmp/host_down.txt
  fi
done
​
[[email protected] test]# chmod a+x ping2.sh
[[email protected] test]# ./10.sh
 Please enter a network segment :192.168.223
[[email protected] test]# cat /tmp/host_down.txt
192.168.223.130 is down
192.168.223.131 is down
192.168.223.133 is down
192.168.223.134 is down
192.168.223.135 is down
192.168.223.136 is down
192.168.223.137 is down
192.168.223.138 is down
192.168.223.139 is down
192.168.223.140 is down
[[email protected] test]# cat /tmp/host_up.txt
192.168.223.132 is up

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

[[email protected] test]# vim iplist
192.168.168.132 22
192.168.168.21 2000
[[email protected] test]# vim 4.sh
#!/bin/bash
num=`cat iplist | wc -l`
for((i=1;i<=$num;i++))
do
  ip=`head -$i iplist | tail -l | awk '{print $1}'`
  port=`head -$i iplist | tail -l | awk '{print $2}'`
  ssh -p $port [email protected]$ip echo 123 | passwd --stdin root
done
[[email protected] test]# chmod a+x 4.sh
[[email protected] test]# ./4.sh