shell学习之for语句的相关练习题

（1）ssh连接三次以上失败则加入到黑名单中

#!/bin/bash
#在/var/log/secure查找连接失败的主机，并统计次数
#累计连接失败超过3次，将此主机加入系统黑名单（/etc/hosts.deny）


[root@server tmp]# cat ssh.sh 
#!/bin/bash

cat /var/log/secure | awk '/Failed/{print $(NF-3)}' | sort | uniq -c | awk '{print $2"="$1}' > /tmp/blacklist

MAXCOUNT="3"

for i in `cat /tmp/blacklist`
do
    IP=`echo $i | awk -F= '{print $1}'`     ##取出主机IP
    NUM=`echo $i | awk -F= '{print $2}'`    ##取出失败次数

if [ $NUM -gt $MAXCOUNT ]; then
    ###屏蔽IP前先确认此IP是否已经存在
    grep $IP /etc/hosts.deny > /dev/null
    if [ $? -gt 0 ]; then
        echo "sshd:$IP" >> /etc/hosts.deny
    fi
fi
done

###然后用ssh连接失败六次

[root@server tmp]# sh ssh.sh 
[root@server tmp]# cat /tmp/blacklist 
172.25.254.19=6
172.25.254.64=1
[root@server tmp]# cat /etc/hosts.deny 

# hosts.deny	This file contains access rules which are used to
#		deny connections to network services that either use
#		the tcp_wrappers library or that have been
#		started through a tcp_wrappers-enabled xinetd.
#
#		The rules in this file can also be set up in
#		/etc/hosts.allow with a 'deny' option instead.
#
#		See 'man 5 hosts_options' and 'man 5 hosts_access'
#		for information on rule syntax.
#		See 'man tcpd' for information on tcp_wrappers
#
sshd:172.25.254.19      ##已经加入到黑名单

（2）创建数据库tom，harry，natasha，并在其中建立表，并备份三个数据库

[root@server tmp]# cat mysql.sh 
#!/bin/bash

MYUSER=root
MYPASS=westos
MYCMD="mysql -u$MYUSER -p$MYPASS"
MYDUMP="mysqldump -u$MYUSER -p$MYPASS"
DBPATH=/home/backup

for dbname in tom harry natasha
do
    $MYCMD -e "create database $dbname"
done
 
[ ! -d "$DBPATH" ] && mkdir -p $DBPATH

for dbname in tom harry natasha
do
    $MYDUMP $dbname | gzip > $DBPATH/${dbname}_$(date +%F).sql.gz
done

for dbname in tom harry natasha
do 
    $MYCMD -e "use $dbname;create table test(id int,name varchar(20));insert into test values(1,'westos');"
done

for dbname in tom harry natasha
do
    echo ========$dbname}.test========
    $MYCMD -e "use $dbname;select * from ${dbname}.test;"
done
[root@server tmp]# sh mysql.sh 
========tom}.test========
+------+--------+
| id   | name   |
+------+--------+
|    1 | westos |
+------+--------+
========harry}.test========
+------+--------+
| id   | name   |
+------+--------+
|    1 | westos |
+------+--------+
========natasha}.test========
+------+--------+
| id   | name   |
+------+--------+
|    1 | westos |
+------+--------+

（3）数据库备份，执行script.sh $dbpasswd 备份数据库中所有库到/mnt/mysqldump目录中，备份文件名称为“库名称.sql”，当此文件存在时进入交互模式，询问动作，输入“s”跳过备份，输入“b”，备份“库名称.sql”为“库名称_backup.sql”,输入“O”时，覆盖原文件,e表示退出

[root@server tmp]# cat mysqldump.sh 
#!/bin/bash

mkdir -p /mnt/mysqldump
DATABASE=`mysql -uroot -pwestos -e "show databases;" | sed '1,2d' | egrep -v "mysql|schema"`

for MYSQL_NAME in $DATABASE
do 
   if [ -e /mnt/mysqldump/${MYSQL_NAME}.sql ]; then
       read -p "${MYSQL_NAME} has been dumped!
       [S]kip [B]ackup [O]verwrite [E]xit
       please input the action:" ACTION
      
       case $ACTION in
       s|S)
       ;;
       b|B)
       mysqldump -uroot -p$1 $MYSQL_NAME > /mnt/mysqldump/${MYSQL_NAME}_backup.sql
       ;;
       o|O)
       mysqldump -uroot -p$1 $MYSQL_NAME > /mnt/mysqldump/${MYSQL_NAME}.s
ql
       ;;
       e|E)
       echo -e "ByeBye~"
       exit 0
       ;;
       esac
    else
       mysqldump -uroot -p$1 $MYSQL_NAME > /mnt/mysqldump/${MYSQL_NAME}.sql
       echo -e "$MYSQL_NAME is backuped!"
    fi
done