一些 Shell 练习

1. 编写脚本实现登陆远程主机。（使用 expect 和 shell 脚本两种形式）。

• expect 形式

[root@Redis-m1:~]#vim expect2.sh 
#!/usr/bin/expect
set HOST [lindex $argv 0]
set USER [lindex $argv 1]
set PASSWORD [lindex $argv 2]
spawn ssh $USER@$HOST
expect {
  "yes/no" { send "yes\n";exp_continue }
  "password" { send "$PASSWORD\n" }
}
interact

[root@Redis-m1:~]#./expect2.sh 192.168.68.71 root cnhope
spawn ssh root@192.168.68.71
The authenticity of host '192.168.68.71 (192.168.68.71)' can't be established.
ECDSA key fingerprint is SHA256:J22pOZ72CGabJHprnwnSFZ6ZHBYuqHKj4avo6PEcaSI.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '192.168.68.71' (ECDSA) to the list of known hosts.
root@192.168.68.71's password: 
Last login: Tue Feb  8 01:23:05 2022 from 192.168.68.21
[root@centos7.9-68.7 ~]#
[root@centos7.9-68.7 ~]#
[root@centos7.9-68.7 ~]#exit

• shell 形式

[root@Redis-m1:~]#vim expect.sh 
#!/bin/bash
HOST=$1
USER=$2
PASSWORD=$3
expect <<EOF
spawn ssh $USER@$HOST
expect {
  "yes/no" { send "yes\n";exp_continue }
  "password" { send "$PASSWORD\n" }
}
expect "]#" { send "ip a\n" }
expect "]#" { send "exit\n" }
expect eof
EOF

[root@Redis-m1:~]#./expect.sh 192.168.68.71 root cnhope
spawn ssh root@192.168.68.71
root@192.168.68.71's password: 
Last login: Tue Feb  8 01:40:33 2022 from 192.168.68.21
[root@centos7.9-68.7 ~]#ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether 00:0c:29:3f:4d:b3 brd ff:ff:ff:ff:ff:ff
    inet 192.168.68.71/24 brd 192.168.68.255 scope global noprefixroute eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::1bc5:53cc:1425:63e7/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever
[root@centos7.9-68.7 ~]#exit
logout
Connection to 192.168.68.71 closed.

2. 生成10个随机数保存于数组中，并找出其最大值和最小值

[root@ubuntu]#vim num.sh
#!/bin/bash
declare -i min max
declare -a nums
for ((i=0;i<10;i++));do
    nums[$i]=$RANDOM
    [ $i -eq 0 ] && min=${nums[0]} && max=${nums[0]}&& continue
    [ ${nums[$i]} -gt $max ] && max=${nums[$i]} && continue
    [ ${nums[$i]} -lt $min ] && min=${nums[$i]}
done
echo "All numbers are ${nums[*]}"
echo Max is $max
echo Min is $min

[root@ubuntu]#bash num.sh 
All numbers are 31880 18437 25248 2610 25194 14211 3525 4138 28762 24368
Max is 31880
Min is 2610

2. 编写脚本，使用for和while分别实现192.168.0.0/24网段内，地址是否能够ping通，若ping通则输出"success!"，若ping不通则输出"fail!"

[root@ubuntu]#cat ping-check1.sh 
#!/bin/bash
for (( i=1;i<=254;i++ ));do
  {
  ping -c1 -W1 192.168.0.${i} >& /dev/null
  if [ $? -eq 0 ];then
    echo 192.168.0.${i} is success!
  else
    echo 192.168.0.${i} is fail!
  fi
  }&
done  
wait

3. 输入若干个数值存入数组中，采用冒泡算法进行升序或降序排序
4. 总结查看系统负载的几种命令，总结top命令的指标大概什么含义(不要求全部写出来)

6. 每周的工作日1:30，将/etc备份至/backup目录中，保存的文件名称格式 为“etcbak-yyyy-mm-dd-HH.tar.xz”，其中日期是前一天的时间。

#1.创建备份脚本
[root@ubuntu]#vim /root/backup.sh
#!/bin/bash
if [ -d /backup ];then
  sleep 1
else
  mkdir /backup
fi
tar -Jcvf /backup/etcbak-`date -d "-1 day" "+%F-%H"`.tar.xz /etc

#2.创建计划任务
[root@ubuntu]#crontab -e
30 1 1-5 * * /bin/bash /root/backup.sh