企业shell面试题及解答

1、面试题：使用for循环在/tmp目录下批量创建10个html文件，其中每个文件需要包含10个随机小写字母加固定字符串template，示例如下

aaesdffbnv_template.html

方法1： 

cd /tmp
for ((i=0;i<10;i++));do touch `echo $RANDOM | md5sum | sed 's/[^a-z]//g' | cut -c 1-10`_template.html;done

方法2：

cd /tmp

for i in `seq 10`;do touch `openssl rand -base64 40 | sed 's/[^a-z]//g' | cut -c 1-10`_template.html;done

2、面试题：批量改名 将以上所得的文件名中的template全部改成leon，并且将html改成大写

方法1：

rename template.html leon.HTML *.html

方法2：

ls *.html | awk -F '_' '{print "mv "$0" "$1"_leon.HTML"}' | bash

3、面试题：批量10个系统账号template01到template10并设置密码（密码为随机数）

方法1：

for i in `seq -w 01 10`;do useradd -M template$i;echo $RANDOM |md5sum  | cut -c 1-10 | tee -a passwd.log | template$i;done

方法2：

echo template{01..10} | tr " " "
" | sed -r 's#(.*)#useradd 1;pass=`echo $RANDOM | md5sum | cut -c 1-10`;echo "$pass"|passwd --stdin 1;echo -e "1	`echo "$pass"`" >> /tmp/passwd.log#g' | bash

方法3：

echo template{01..10} | xargs -n1 useradd;echo template{01..10}:`cat /dev/urandom|tr -dc 0-9|fold -w8|head -1` | xargs -n1|tee -a pass.txt|chpasswd

4、面试题：写一个脚本，判断192.168.8.0/24网路里，当前在线的IP有哪些

方法1：

#!/bin/bash                                                                                                                         G
for i in `seq 254`
do
    {   
    ping -c 2 -W 2 192.168.8.$i &>/dev/null
    if [ $? -eq 0 ];then
        echo "192.168.8.$i is alive"                                                                                                ?
    fi                                                                                                                              ?
}&                     #shell的并发检测功能，批量ping，快速返回结果
done 

方法2：使用namp（需要安装namp）

nmap -sP 192.168.8.0/24 | awk '/Nmap scan report for/{print $NF}'    #1到2秒返回结果

5、面试题：写一个shell脚本以解决DDOS攻击生产的问题

请根据Web日志或网络连接数，监控当某个IP并发连接数或短时间内PV达到100时，即调用防火墙命令封掉该对应的IP：防火墙的命令为：

iptables -I INPUT -s IP -j DROP

 参考此脚本：

#!/bin/bash
#Author Template
#Time 2018-07-02 22:06
file=$1
log_file=/tmp/tmp.log


JudgeExt(){
    if expr "$1" : ".*.log" &> /dev/null;then
        :
    else
        echo "Usage: $0 xxx.log"
        exit 1
    fi
}

IpCount(){

    grep "ESTABLISHED" $1 | gawk -F "[ :]+" '{++S[$(NF-3)]} END {for (key in S) print S[key],key}' | sort -rn -k1 | head -5 > $log_file

}

ipt(){
    local ip=$1
    if [ `iptabls -L -n | grep "$ip" | wc -l` -lt 1 ];then
        iptabls -I INPUT -s $ip -j DROP
        echo "$line  is dorpped" >> /tmp/drop_list_$(date +%F).log
    fi

}

main(){

    JudgeExt $file 
    while true
    do
        IpCount $file
        while read line
        do
            ip=`echo $line | gawk '{print $2}'`
            count=`echo $line | gawk '{print $1}'`
            if [ $count -gt 500 ];then
                ipt $ip
            fi
        done < $log_file
        sleep 180

    done
}
main

 6、面试题：请用脚本实现Mysql数据库分库备份

#!/bin/bash
echo -e [`date +"%Y-%m-%d %H:%M:%S"`] start
#system time
time=`date +"%y-%m-%d"`
#host IP
host="127.0.0.1"
#database backup user
user="root"
#database password
passwd="yourpasswd"
#Create a backup directory
mkdir -p /backup/db/"$time"
#list database name
all_database=`/usr/bin/mysql -u$user -p$passwd -Bse 'show databases'`
#in the table from the database backup
for i in $all_database
do
/usr/bin/mysqldump -u$user -p$passwd $i > /backup/db/"$time"/"$i"_"$time".sql
done
echo -e [`date +"%Y-%m-%d %H:%M:%S"`]  end
exit 0

7、面试题：请用脚本实现Mysql数据库分库分表备份

#!/bin/bash
PATH="/application/mysql/bin:$PATH"
DBPATH=/server/backup
MYUSER=root
MYPASS=123456
SOCKET=/data/3306/mysql.sock
MYCMD="mysql -u$MYUSER -p$MYPASS -S $SOCKET"
MYDUMP="mysqldump -u$MYUSER -p$MYPASS -S $SOCKET"
[ ! -d "$DBPATH" ] && mkdir $DBPATH

for dbname in `$MYCMD -e "show database;" | sed '1,2d' | egrep -v "mysql|schema"`
do
    mkdir $DBPATH/${dbname}_$(date +%F) -p
    for table in `$MYCMD -e "show tables from $dbname;"| sed '1d'`
    do  
        $MYDUMP $dbname $table | gzip > $DBPATH/${dbname}_$(date +%F)/${dbname}_${table}.sql.gz
    done
done

8、面试题：请开发一个shell脚本，比较两个整数的大小，通过传参的方式

#!/bin/bash

a=$1
b=$2

Usage(){

echo "Usage:$0 NUM1 NUM2"
exit 2
}

[ $# -ne 2 ] && { ##判断传参个数
Usage
}

expr $a + 1 &> /dev/null #使用expr只能计算两个整数的原理，判断传入的参数是否为整数
RETVAL_A=$?
expr $b + 1 &> /dev/null
RETVAL_B=$?

[ $RETVAL_A -ne 0 -o $RETVAL_B -ne 0 ] && {

echo "you must input integer "
exit 1
}

if [ "$a" -lt "$b" ];then
echo "$a < $b"
elif [ "$a" -gt "$b" ];then
echo "$a > $b"
else
echo "$a = $b"
fi
exit 0

 9、面试题：打印选择菜单，按照选择一键安装不同的web服务

#!/bin/bash
PS3="Enter option: "                #设置提示符
stty erase ^h                           #设置退格删除键为backspace
trap "echo Goodbye..." EXIT     #检测到exit信号，输出Goodbye
select option in "install LNMP" "install LANP" "Exit"
do
    case $option in
        "install LNMP")
            sh install_lnmp.sh
            ;;  
        "install LANP")
            sh install_lamp.sh
            ;;  
        "Exit")
            exit
            ;;  
        *)  
            echo "123"
            ;;  
        esac
done                        

10、Web及Mysql服务异常监测

 网站监测：

#!/bin/bash
#Author Template
#Time 2018-07-01 16:00
url_list=(
http://www.cnblogs.com/Template/
http://www.baidu.com
http://127.0.0.1
)

. /etc/init.d/functions
function wait(){

    echo -n "3 秒后执行检查."
    for ((i=0;i<3;i++))
    do
        echo -n "." ;sleep 1
    done
    echo
}


function check_url(){
    wait
    for ((i=0;i<`echo ${#url_list[*]}`;i++))
    do
        wget -o /dev/null -T 3 --tries=1 --spider ${url_list[$i]} &> /dev/null
        if [ $? -eq 0 ];then
            action "${url_list[$i]}" /bin/true
        else
            action "${url_list[$i]}" /bin/false

        fi
        ((check_count++))
    done
    }

main(){
    while true
    do
        check_url
        echo "------------check count:${check_count}------------------"
        sleep 10
    done

}
main

Mysql监测：

方法1：

#!/bin/bash
if [ "`netstat -tlunp  | grep 3306 | awk -F "[ :]+" '{print $4}'`" = "3306" ];then
    echo "Mysql is Running"
else
    echo "Mysql is Stopped"
    /etc/init.d/mysqld start
fi

方法2：

#!/bin/bash
if [ `netstat -tlunp | grep "3306" | wc -l`  -gt 0 ];then
    echo "Mysql is Running"
else
    echo "Mysql is Stopped"
    /etc/init.d/mysqld start
fi

方法3：

#!/bin/bash
if [ `lsof -i tcp:3306 | wc -l`  -gt 0 ];then
    echo "Mysql is Running"
else
    echo "Mysql is Stopped"
    /etc/init.d/mysqld start
fi

11、面试题：写出网络服务独立进程模式下Rsync的系统启动脚本，例如：/etc/init.d/rsyncd {start|stop|restart}

#!/bin/bash
# chkconfig: 2345 20 80
#description Rsyncd start stop script

. /etc/init.d/functions 

function Usage(){
    echo "Usage:$0 {start | stop | restart}"
    exit 1
}

function start (){
    rsync --daemon
    sleep 1

    if [ `netstat -tlunp | grep rsync | wc -l` -ge 1 ];then
        action "rsyncd  started" /bin/true
    else
        action "rsyncd started" /bin/false
        exit 1
    fi  
}
    
function stop(){ 
    killall rsync &> /dev/null
    sleep 1
    if [ `netstat -tlunp | grep rsync|wc -l` -eq 0 ];then
        action "rsyncd stopped" /bin/true
    else
        action "rsyncd stopped" /bin/false
        exit 1
    fi  
}

function restart(){
    stop && start
}

case "$1" in
    "start")
            start
            ;;
    "stop")
            stop
            ;;
    "restart")
            restart
            ;;
        *)
            Usage
esac

12、面试题：请写出mysql多实例启动脚本

#!/bin/bash
port=3306
mysql_user="root"
mysql_pwd="123456"
CmdPath="/application/mysql/bin"
mysql_sock="/data/${port}/mysql.sock"
. /etc/init.d/functions

start(){
    if [ ! -e "$mysql_sock" ];then
         printf "Starting MySQL...
"
        /bin/sh ${CmdPath}/mysqld_safe --defaults-file=/data/${port}/my.cnf 2>&1 > /dev/null &
    [ $? -eq 0 ] && action "Mysql start" /bin/true || action "Mysql start" /bin/false
    else
        printf "MySQL is running...
"
        exit 1
    fi
}

stop(){
    if [ ! -e "$mysql_sock" ];then
        printf "MySQL is stopped...
"
        exit 1
    else
        printf "Stoping MySQL...
"
        ${CmdPath}/mysqladmin -u ${mysql_user} -p${mysql_pwd} -S /data/${port}/mysql.sock shutdown
    [ $? -eq 0 ] && action "Stop mysql" /bin/true || action "Stop mysql" /bin/false 
    fi
}

restart(){
    printf "Restarting MySQL...
"
    stop
    sleep 2
    start
}

Usage(){
    echo "Usage: /data/${port}/mysql (start|stop|restart)"
    exit 1
}


case "$1" in

start)
    start
    ;;
stop)
    stop
    ;;
restart)
    restart
    ;;
*)
    Usage
    ;;
esac