• Bash shell编程实例


     

    Linux运维之Shell编程实例

    题目1:监控MySQL错误码及主从复制同步异常;

    监控MySQL主从同步是否异常,如果异常,则发送短信或者邮件给管理员。提示:如果没主从同步环境,可以用下面文本放到文件里读取来模拟:
    阶段1:开发一个守护进程脚本每30秒实现检测一次;
    阶段2:如果同步出现如下错误号(1158,1159,1008,1007,1062),则跳过错误;
    阶段3:请使用数组技术实现上述脚本(获取主从判断及错误号部分)。

    阶段1:
    */2 * * * * user /PATH/TO/SCRIPT


    阶段2:监控MySQL-----过滤错误码;

    #!/bin/bash
    CONTACT='root@node77'
    ERR_LOG='/var/log/mariadb/mariadb.log'

    yum install mailx -y
    email_to_admin() {
    mailsubject="MySQL Error."
    mailbody="`date +%F-%H:%M:%S`: MySQL Error,please check and repair."
    echo $mailbody | mail -s "$mailsubject" $CONTACT
    }

    while true;do
    for ERROR_CODE in `grep 'Error_code: [[:digit:]]+' $ERR_LOG | grep -o '[[:digit:]]+'` ;do
    case $ERROR_CODE in
    1007) 
    continue
    ;;
    1008) 
    continue
    ;;
    1158)
    continue
    ;;
    1159) 
    continue
    ;;
    1162) 
    continue
    ;;
    esac
    email_to_admin
    done
    sleep 30
    done


    阶段3:监控MySQL-----主从同步;

    #!/bin/bash
    DB_USER='root'
    DB_PASSWORD='cured'
    DB_PORT='3306'
    MASTER='192.168.0.76'
    SLAVE='192.168.0.77'
    CMD_CONN_MASTER='mysql -u$DB_USER -p$DB_PASSWORD -P$DB_PORT -h$MASTER'
    CMD_CONN_SLAVE='mysql -u$DB_USER -p$DB_PASSWORD' -P$DB_PORT -h$SLAVE'
    CONTACT='root@node77'

    declare -a master_status
    master_status[0]="CMD_CONN_MASTER -e 'show master statusG' | egrep File | cut -d: -f2"
    master_status[1]="CMD_CONN_MASTER -e 'show master statusG' | egrep Position | cut -d: -f2"

    declare -a slave_status
    slave_status[0]="CMD_CONN_SLAVE -e 'show slave statusG' | egrep Master_Log_File | cut -d: -f2"
    slave_status[1]="CMD_CONN_SLAVE -e 'show slave statusG' | egrep Read_Master_Log_Pos | cut -d: -f2"
    slave_status[2]="CMD_CONN_SLAVE -e 'show slave statusG' | egrep Last_Errno | cut -d: -f2"

    email_to_admin() {
    mailsubject="Syncing failed."
    mailbody="`date '+%F %H:%M:%S'`: Syncing of master-slave is failed,please check and repair."
    echo $mailbody | mail -s "$mailsubject" $CONTACT
    }

    while true ; do
    if [ ${master_status[0]} == ${slave_status[0]} -a ${master_status[1]} == ${slave_status[1]} -a ${slave_status[2]} == 0 ]; then 
    echo "Syncing of master-slave is OK."
    else
    echo "Syncing of master-slave is failed." 
    email_to_admin
    fi
    sleep 30
    done

    题目2:批量创建、重命名文件;
    (1)使用for循环在/heros目录下通过随机小写10个字母加固定字符串_yangkang批量创建10个html文件,名称例如为:
    (2)将上述各文件名中的yangkang改为yangguo,并将html改成大写。

    #!/bin/bash
    #批量创建随机名称的文件
    HTML_DIR=/heros
    [ ! -d $PATH ] && mkdir $HTML_DIR
    #yum isntall coreutils -y 
    #[ ! -d $PATH ] && install -m 700 -d $HTML_DIR
    #使用install创建目录时,需安装coreutils。
    cd $HTML_DIR && for i in `seq 10` ; do touch `openssl rand -base64 64 | tr -dc a-z | head -c 10`_yangkang.html; done

    #!/bin/bash
    #批量重命名文件
    HTML_DIR=/heros
    FILES=`ls $HTML_DIR`
    GUO=guo.HTML
    YANGGUO=_yangguo.HTML

    cd $HTML_DIR && for j in $FILES; do 
    CHARS=`echo $j | cut -c 1-15`
    mv $CHARS* $CHARS$GUO
    done

    cd $HTML_DIR && for j in $FILES; do 
    CHARS=`echo $j | awk -F '_' '{print$1}'`
    mv $CHARS* $CHARS$YANGGUO
    done


    类似题目:批量创建用户;
    批量创建10个系统帐号user01-user10,并设置密码为随机8位字符串。

    #!/bin/bash
    #批量创建用户,密码随机
    for i in {01..10}; do 
    PASSWORD=`tr -dc [:alpha:] < /dev/urandom | head -c 8`
    #PASSWORD=`openssl rand -base64 16 | tr -dc [[:alpha:]] | head -c 8`
    useradd user$i 
    echo $PASSWORD | passwd --stdin user$i
    echo user$i-----$PASSWORD >> /tmp/user-pwd.txt
    done

    for j in {01..10}; do userdel -r user$j; done

    题目3:判断在线主机;
    写一个脚本,实现判断10.0.0.0/24网络里,当前在线用户的IP有哪些。

    #!/bin/bash
    #

    declare -i i=1
    declare -i online
    declare -i offline
    net="10.0.0."

    while [ i -le 254 ]; do
    ping $net$i -c2 -w2 &> /dev/null
    if [ $? -eq 0 ];then
    echo "$net$i is on-line."
    let online++
    else 
    echo "$net$i is off-line."
    let offline++
    fi
    let i++
    done

    echo "NO. of on-line hosts: $online ."
    echo "NO. of off-line hosts: $offline ."

    题目4:监控并发连接;
    写一个脚本解决DOS攻击生产案例。
    提示:根据web日志或者或者网络连接数,监控当某个IP并发连接数或者短时内PV达到100,即调用防火墙命令封掉对应的IP,监控频率每隔3分钟。防火墙命令为:iptables -I INPUT -s 10.0.1.10 -j DROP。

    #!/bin/bash

    IPlist=`netstat -ntu | awk 'NR>2' | awk '{print $5}' | cut -d: -f1 | uniq -c | sort | awk '{if($1>99)print $2}'`
    #测试时,使用的并发连接为2,实际生产可将NR>2改为>100;

    for ip in $IPlist; do
    iptables -I INPUT -s $ip -j DROP
    echo "$IPlist is dropped."
    sleep 180
    done

    题目5:服务启动脚本;
    开发mysql多实例启动脚本:
    已知mysql多实例启动命令为:mysqld_safe--defaults-file=/data/3306/my.cnf &
    停止命令为:mysqladmin -u$MYSQL_USER -p$MYSQL_PASSWORD -S /data/3306/mysql.sock shutdown
    请完成mysql多实例启动启动脚本的编写。
    要求:用函数,case语句、if语句等实现。

    #!/bin/bash
    . /etc/init.d/functions

    declare -a PORT
    PORT=(3306 3307 3308 3309 3310)
    MYSQL_SOCK=/data/$PORT/mysql.sock

    for i in (3306..3310); do echo $i; done

    start() {
    if [ ! e "MYSQL_SOCK" ]; then
    nohub mysqld_safe--defaults-file=/data/${PORT[$i]}/my.cnf > /dev/null 2>&1 &
    ss -tun | grep :${PORT[$i]}
    if [ $? -eq 0 ]; then 
    action "Mysql of ${PORT[$i]} is listening." /bin/true
    else
    action "Mysql of ${PORT[$i]} isn't listening" /bin/false
    fi
    else
    action "Mysql of ${PORT[$i]} is listening already." /bin/false

    }

    stop() {
    if [ e "MYSQL_SOCK" ]; then
    nohub mysqladmin -u$MYSQL_USER -p$MYSQL_PASSWORD -S /data/$PORT/mysql.sock shutdown > /dev/null 2>&1 & 
    ss -tun | grep :$PORT{PORT[$i]}
    if [ $? -ne 0 ]; then 
    action "Mysql of $PORT has been stopped." /bin/true
    else
    action "Mysql of $PORT is still listening." /bin/false
    fi
    else
    action "Mysql of $PORT has been stopped already." /bin/false

    }

    case "$1" in
    start)
    start
    ;;
    stop)
    stop
    ;;
    restart)
    stop
    start
    ;;
    *)
    echo "Usage:$0 {3306|3307|3308|3309|3310}{start|stop|restart}"
    ;;
    esac


    类似题目:rsyncd服务启动脚本;
    撰写脱离xinetd服务,独立进程运行模式下rsync的服务启动脚本;
    例如:/etc/init.d/rsyncd{start|stop|restart}
    要求:使用函数、可被chkconfig管理;

    #!/bin/bash
    # chkconfig: 2345 75 25
    # describtion: This service starts|stops|restarts rsync server daemon.

    . /etc/rc.d/init.d/functions

    prog=$(basename $0)
    lockfile=/var/lock/subsys/$prog

    start() {
    if [ -e $lockfile ]; then
    action "Rsyncd is running already." /bin/false
    else
    touch $lockfile
    action "Starting rsyncd finished." /bin/true

    fi
    }

    stop() {
    if [ -e $lockfile ]; then
    rm -f $lockfile
    action "Stopping rsyncd finished." /bin/true
    else
    action "Rsyncd is stopped already." /bin/false
    fi
    }

    status() {
    if [ -e $lockfile ]; then
    echo "Rsyncd is running."
    else
    echo "Rsyncd is stopped."
    fi
    }

    usage() {
    echo "Usage:$prog {start|stop|status|restart}"
    }

    if [ $# -ne 1 ]; then
    usage
    exit
    fi

    case $1 in
    start)
    start
    ;;
    stop)
    stop
    ;;
    status)
    status
    ;;
    restart)
    stop
    start
    ;;
    *)
    usage
    ;;
    esac

    题目6:打包备份;
    如何实现对MySQL数据库进行分库加分表备份,请用脚本实现。


    #!/bin/bash
    yum install expect -y

    DATE=`date +%Y-%m-%d`
    OLD_DATE=`date +%Y-%m-%d -d '-30 days'`
    BAK_DIR=/backup/mydata
    DB_USER=root
    DB_PASSWORD=cured
    DB_name=DB_NAME
    table_name=TABLE_NAME


    [ -d ${BAK_DIR} ] || mkdir -p ${BAK_DIR}
    [ -d ${BAK_DIR}/${DATE} ] || mkdir ${BAK_DIR}/${DATE}
    [ ! -d ${BAK_DIR}/${OLD_DATE} ] || rm -rf ${BAK_DIR}/${OLD_DATE}

    for DB_NAME in mysql $DB_NAME $TABLE_NAME
    do
    /usr/bin/mysqldump -u$DB_USER -p$DB_PASSWORD --databases ${DB_NAME} > ${BAK_DIR}/${DATE}/${DATE}-${DB_NAME}-backup.sql
    /bin/sleep 3
    done

    cd ${BAK_DIR}
    tar -cjf $DATE.db_bak.tar.bz2 $DATE
    /bin/sleep 3

    password='cured'
    #System user's password for root@DB_BAK_SERVER
    expect -c "
    spawn scp $DATE.db_bak.tar.bz2 root@DB_BAK_SERVER:/backup/mydata
    expect {
    "yes/no" {set timeout 30; send "yes "; exp_continue;}
    "password" {set timeout 30; send "$password ";} 
    }
    expect eof"
    #####本脚本实现MySQL服务器打包压缩备份,并自动交互上传至备份服务器,分库分表备份暂未实现。#####

    题目7:字符串打印; 
    使用for循环打印下面这句话中字母数不大于6的单词。
    I am an interviewer, welcome to our company for interviewing .

    #!/bin/bash

    WORDS='I am an interviewer welcome to our company for interviewing'

    for i in $WORDS; do
    NUM= `echo $i | wc -L`
    if [ $NUM -le 6 ]; then
    echo $i
    fi
    done

    for i in $WORDS; do
    if [ ${#i} -le 6 ]; then
    echo $i
    fi
    done


    类似题目:字符串处理;
    中启动力shell面试题:
    1、按单词出现频率降序排序!
    2、按字母出现频率降序排序!
    the squid project provides a number of resources toassist users design,implement and support squid installations. Please browsethe documentation and support sections for more infomation

    #!/bin/bash
    WORDS='the squid project provides a number of resources toassist users design implement and support squid installations Please browsethe documentation and support sections for more infomation'

    for i in $WORDS; do echo $i; done | sort | uniq -c | sort -rn


    #!/bin/bash
    WORDS='the squid project provides a number of resources toassist users design implement and support squid installations Please browsethe documentation and support sections for more infomation'

    for i in $WORDS; do
    for j in `seq 1 ${#i}`; do
    ALPHA=`echo $i | cut -c$j`
    echo $ALPHA
    done
    done | sort | uniq -c | sort -rn

    题目8:判断数字大小;
    开发shell脚本,分别实现以脚本传参以及read读入的方式比较2个整数大小。以屏幕输出的方式提醒用户比较结果。注意:一共是开发2个脚本。当用脚本传参以及read读入的方式需要对变量是否为数字、并且传参个数做判断。


    #!/bin/bash
    ##########以脚本传参,非read读入方式(执行脚本时,在命令后面跟两个参数)##########

    [ ! $# -ne 2 ] && {
    echo "You should input 2 integer nums after run $0 next time,bye."
    exit 1
    }

    expr $1 + 1 &> /dev/null
    RETVAL_A=$?
    expr $2 + 2 &> /dev/null
    RETVAL_B=$?
    [ $RETVAL_A -ne 0 -o $RETVAL_B -ne 0 ] && {
    echo "At least one of numbers you input isn't integer num."
    exit 2
    }

    if [ $1 -lt $2 ] ; then
    echo "$1 < $2" 
    elif [ $1 -eq $2 ] ; then
    echo "$1 = $2"
    else
    echo "$1 > $2"
    fi


    #!/bin/bash
    ##########read读入方式##########
    read -t 10 -p "Please input one integer nums: " a
    if [ -z $a ];then
    echo "2B,Bye." && exit 1
    fi

    read -t 10 -p "Please input the other integer nums: " b
    if [ -z $b ];then
    echo "2B,Bye." && exit 1
    fi

    expr $a + 1 &> /dev/null
    RETVAL_A=$?
    expr $b + 2 &> /dev/null
    RETVAL_B=$?
    [ $RETVAL_A -ne 0 -o $RETVAL_B -ne 0 ] && {
    echo "At least one of numbers you input isn't integer num."
    exit 2
    }

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

    题目9:打印菜单;
    打印选择菜单,一键安装web服务;
    [root@node25 ~ ]# sh menu.sh
    1.[install lamp]
    2.[install lnmp]
    3.[exit]
    Please select an pition:

    要求:
    1、当用户输入1时,输出“start to install lamp.”然后执行/server/scripts/lamp.sh,脚本内容输出"lamp is installed"后退出脚本;
    2、当用户输入2时,输出“start to install lnmp.”然后执行/server/scripts/lnmp.sh输出"lnmp is installed"后退出脚本;
    3、当输入3时,退出当前菜单及脚本;
    4、当输入任何其它字符,给出提示“Input error”后退出脚本;
    5、要对执行的脚本进行相关条件判断,例如:脚本是否存在,是否可执行等。

    #!/bin/bash

    cat << EOF
    1.[install lamp]
    2.[install lnmp]
    3.[exit]
    ============================
    EOF

    read -p "Please select an pition: " option
    while [ "$option" != '1' -a "$option" != '2' -a "$option" != '3' ]; do
    read -p "Wrong option, select again: " option
    done

    if [ "$option" == '1' ]; then
    echo "Start to install lamp."
    echo "Lamp is installed."
    exit 1
    elif [ "$option" == '2' ]; then
    echo "Start to install lnmp."
    echo "Lnmp is installed."
    exit 2
    else
    echo "Exit"
    exit 3
    fi
    #####最后的if多分支条件语句也可改为以下的case条件语句。#####
    case $option in 
    1)
    echo "Start to install lamp."
    echo "Lamp is installed."
    exit 1
    ;;
    2)
    echo "Start to install lnmp."
    echo "Lnmp is installed."
    exit 2
    ;;
    3)
    echo "Exit" 
    exit 3
    ;;
    *)
    echo "Usage:{1|2|3|}"
    exit 4
    ;;
    case

    题目10:监控web和DB服务;
    要求:1、分别监控web和DB服务是否正常,各不低于3种监控策略;2、间隔1分钟,持续监控。

    监控web法一:80端口;
    ss -tanl | grep :80 | uniq | wc -l
    netstat -tanl | grep :80 | uniq | wc -l

    监控web法二:http状态码,正常访问时为200;
    yum install curl -y
    curl -I -s -o /dev/null -w %{http_code} $WEB_SVR_URL
    -I, --head Show document info only
    -m, --max-time SECONDS
    -o /dev/null, --output FILE to /dev/null
    -s, --silent Silent mode
    -w %{http_code},-w, --write-out FORMAT What to output after completion

    yum install wget -y
    wget -S -T 10 --spider $WEB_SVR_URL 2>&1 | grep "200" | awk '{print $2}'
    -S, --server-response print server response.
    --spider don't download anything.
    -T, --timeout=SECONDS

    监控web法三:web进程,这里以httpd为例;
    ps -ef | grep httpd | grep -v grep | uniq | wc -l


    #!/bin/bash

    PORT_NUMS=`ss -tanl | grep :80 | uniq | wc -l`
    #PORT_NUMS=`netstat -tanl | grep :80 | uniq | wc -l`
    CONTACT='root@node77'
    email_to_admin() {
    mailsubject="Web Down."
    mailbody="`date '+%F %H:%M:%S'`: Web service is unavailable,please check and repair."
    echo $mailbody | mail -s "$mailsubject" $CONTACT
    }

    if [ $PORT_NUMS -eq 0 ]; then
    echo "Web service is unavailable."
    mail_to_admin
    else
    echo "Web service works correctly."
    fi


    #!/bin/bash
    yum install curl wget -y
    WEB_SVR_URL="http://192.168.0.76/index.html"
    STATUS_CODE=`curl -I -s -o /dev/null -w %{http_code} $WEB_SVR_URL`
    #STATUS_CODE=`wget -S -T 10 --spider $WEB_SVR_URL 2>&1 | grep "200" | awk '{print $2}'`
    CONTACT='root@node77'
    email_to_admin() {
    mailsubject="Web Down."
    mailbody="`date '+%F %H:%M:%S'`: Web service is unavailable,please check and repair."
    echo $mailbody | mail -s "$mailsubject" $CONTACT
    }

    if [ $STATUS_CODE == "200" ]; then
    echo "Web service works correctly."
    else
    echo "Web service is unavailable."
    mail_to_admin
    fi

    #!/bin/bash
    PID_NUMS=`ps -ef | grep httpd | grep -v grep | uniq | wc -l`
    CONTACT='root@node77'
    email_to_admin() {
    mailsubject="Web Down."
    mailbody="`date '+%F %H:%M:%S'`: Web service is unavailable,please check and repair."
    echo $mailbody | mail -s "$mailsubject" $CONTACT
    }

    if [ $PID_NUMS -eq 0 ]; then
    echo "Web service is unavailable."
    mail_to_admin
    else
    echo "Web service works correctly."
    fi


    监控DB法一:监听端口(以MySQL或MariaDB为例);
    DB_PORT=`ss -tanl | grep :3306 | awk '{print $4}' | cut -d: -f2`
    if [ $DB_PORT == "3306" ]; then
    echo "Database service works correctly."
    ......


    监控DB法二:sock文件(以MySQL或MariaDB为例);
    DB_HOME="/var/lib/mysql/"
    DB_SOCK="mysql.sock"
    SOCK_FILE=`ls -l $DB_HOME$DB_SOCK`

    if [ -e $SOCK_FILE ]; then
    echo "Database service works correctly."
    ......


    监控DB法三:DB进程(以MySQL或MariaDB为例);
    DB_PID_NUMS=`ps -ef | grep mysql | grep -v grep | uniq | wc -l`
    DB_PID_NUMS=`ps -ef | grep mariadb | grep -v grep | uniq | wc -l`
    if [ $DB_PID_NUMS -gt 0 ]; then
    echo "Database service works correctly."
    ......

    题目11:监控memcache服务;
    监控memcached服务是否正常,模拟用户(web客户端)检测;
    使用nc命令加上set/get来模拟检测,以及监控响应时间及命中率。

    #!/bin/bash
    mem_srv=`ss -tunl | grep :11211 | wc -l`
    log_path=/monitor/memcached
    #email_of_admin=username@domain

    if [ ! -d $log_path ]; then
    mkdir -p $log_path
    fi

    if [ $mem_srv -gt 0 ]; then
    printf "set test_key 0 3600 5 hello " | nc 127.0.0.1 11211 &> /dev/null
    retn_code_1=`echo $?`
    printf "get test_key " | nc 127.0.0.1 11211 &> /dev/null
    retn_code_2=`echo $?`
    printf "delete test_key " | nc 127.0.0.1 11211 &> /dev/null
    retn_code_3=`echo $?`

    if [ $retn_code_1 -eq 0 -a $retn_code_2 -eq 0 -a $retn_code_3 -eq 0 ]; then
    echo "Memcached service is OK."

    num_of_get_hits=`printf "stats " | nc 127.0.0.1 11211 | grep "get_hits" | awk '{print $3}'`
    num_of_cmd_get=`printf "stats " | nc 127.0.0.1 11211 | grep "cmd_get" | awk '{print $3}'`
    get_hit_rate=`awk 'BEGIN{printf "%.2f% ",('$num_of_get_hits'/'$num_of_cmd_get')*100}'`
    echo "The get_hit_rate is : $get_hit_rate ."
    fi

    else
    echo "Memcached service is down at `date +%F-%H:%M:%S`." | tee ${log_path}/error.log
    # mail -s "Memcached service is down at `date +%F-%H:%M:%S`." $email_of_admin
    fi



    题目12:监控文件安全;
    监控web文件是否被篡改,如果被篡改,则告警并且发邮件;每3分钟检查一次。

    思路:Web上线后,使用md5sum命令对整个web目录中的所有文件生成相应地md5码,保存在/md5db/web/original.txt中。以后的md5码保存在/md5db/web/current.txt中,
    被篡改的文件信息保存在/md5db/web/different.txt中。

    #!/bin/bash
    WEB_DIR="/var/www/html"
    DATE=`date +%F`
    TIME=`date +%H:%M:%S`
    [ ! -d /md5db/web ] && mkdir -p /md5db/web
    md5sum $WEB_DIR/* > /md5db/web/current.txt 
    diff /md5db/web/original.txt /md5db/web/current.txt > /md5db/web/different.txt
    if [ ! $? -eq 0 ]; then
    echo -e "33[41;37m Warning!web files have been altered at $DATE $TIME.33[0m"
    cat /md5db/web/different.txt
    # mail_to_amin
    else
    echo "Relax,web files are not be altered."
    fi

    crontab -e
    */20 * * * * root bash /bashs/md5db.sh

    题目13:抓阄;
    有N个学生,选3个参加实践;
    要求:
    1、执行脚本时,想去的同学输入姓名后,随机产生1-99之间的数字,数字最大的3人参加实践,已抓到的数字,下次不能再出现;
    2、第一个名字输入后,屏幕输出信息,并将名字和数字记录到文件中,程序不能退出继续等待别的学生输入。

    #!/bin/bash

    NAME_LIST="/tmp/name_list.txt"
    >$NAME_LIST
    STU_NUMS=9

    read_name(){
    read -p "Please enter your name: " name
    if [ -z $name ]; then
    echo "Nothing input."
    read_name
    else
    if [ `egrep -w "$name" $NAME_LIST | wc -l` -gt 0 ]; then
    echo "This name is already in-use."
    read_name
    fi
    if [ `egrep -w "$(echo $[$RANDOM%99+1])" $NAME_LIST | wc -l` -gt 0 ]; then
    echo "This number is already in-use."
    read_name
    fi
    if [ `egrep -w "$name" $NAME_LIST | wc -l` -eq 0 ] && [ `egrep -w "$(echo $[$RANDOM%99+1])" $NAME_LIST | wc -l` -eq 0 ]; then
    echo "`echo $[$RANDOM%99+1]` $name" >> $NAME_LIST
    fi
    fi
    }

    while [ `cat $NAME_LIST | sort -rn -k1 | wc -l` -le $STU_NUMS ]; do
    read_name
    done

    echo "The loting is ended, the results are as fallows: "
    cat $NAME_LIST | sort -rn -k1 | head -3

    #循环从0开始,这里表示学生数目的变量值为:学生总人数-1;
    #随机产生1-99之间的数字,在使用RANDOM系统内置变量时需要用:数字最大值+1,如[$RANDOM%99+1](也就是[$RANDOM%100])。

    题目14:检查网站地址是否正常;
    https://www.aliyun.com
    http://download.cirros-cloud.net
    http://nginx.org
    http://61.135.169.125
    要求使用数组。

    #!/bin/bash
    declare -a urls
    urls=(
    "https://www.aliyun.com"
    "http://download.cirros-cloud.net"
    "http://nginx.org"
    "http://61.135.169.125"
    )

    while true; do
    for ((i=0;i<${#urls[*]};i++)); do
    wget --spider --timeout=6 --tries=3 ${urls[$i]} &> /dev/null
    if [ $? -eq 0 ]; then
    echo "${urls[$i]} is OK."
    else
    echo "${urls[$i]} is down."
    fi
    sleep 3
    done
    done

    题目15:暴力破解加密字符串;
    已知下面的字符串是通过RANDOM随机数变量md5sum|cut -c 1-8截取后的结果,请破解这些字符串对应的md5sum前的RANDOM对应数字?
    21029299
    00205d1c
    a3da1677
    1f6d12dd

    #!/bin/bash
    rand_str=(
    21029299
    00205d1c
    a3da1677
    1f6d12dd
    )

    for ((i=0;i<32768;i++)); do
    for ((j=0;j<${#rand_str[*]};j++)); do
    if [ "`echo $i | md5sum | cut -c1-8`" == "${rand_str[$j]}" ]; then
    echo $i ${rand_str[$j]} 
    fi
    done
    done

    结果:
    1346 00205d1c
    7041 1f6d12dd
    25345 a3da1677
    25667 21029299

     
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  • 原文地址:https://www.cnblogs.com/huangguabushihaogua/p/12161410.html
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