Linux Shell 脚本经典案例（一）

编写Shell过程中注意事项
1 开头加解释器：#!/bin/bash
2 语法缩进，使用四个空格，多加注释说明
3 命名建议规则：变量名大写，局部变量小写，函数名小写，名字体现出实际作用。
4 默认变量是全局的，在函数中变量local指定为局部变量，避免污染其他作用域。
5 调试脚本命令：set -e 遇到执行非0时，退出脚本，set -x 打印执行过程。
6 写脚本一定先到测试环境，再到生产环境上。

1 获取随机字符串或数字
1）获取随机8位字符串：

方法1 
]# echo $RANDOM |  md5sum | cut -c 1-8
方法2
]# openssl rand -base64 4
方法3 
]# cat /proc/sys/kernel/random/uuid | cut -c 1-8

2）获取随机8位数字

方法1 
]# echo $RANDOM | cksum | cut -c 1-8  //cksum：打印CRC校验和统计字节
方法2 
]# openssl rand -base64 4 | cksum | cut 1-8
方法3 
]# date +%N | cut -c 1-8

2 定义一个颜色输出字符串函数
方法1

function echo_color() {
    if [ $1 == "green" ];then
        echo -e "\033[32;40m$2\033[0m"
    elif [ $1 == "red" ]; then
        echo -e "\033[32;40m$2\033[0m"
    fi
}

方法2

function echo_color() {
    case $1 in
        green)
            echo -e "[32;40m$2[0m"
            ;;
        red)
            echo -e "[32;40m$2[0m"
            ;;
        *)
            echo "Example:echo_color red string"
    esac
}

3 批量创建用户

#! /bin/bash
DATE = $(date +%F_%T)
USER_FILE=user.txt
echo_color(){
    if [ $1 == "green" ];then
        echo -e "[32;40m$2[0m"
    elif [ $1 == "red" ];then
        echo -e "[32;40m$2[0m"
    fi
}

#如果用户文件存在并大小大于0就备份

if [ -s $USER_FILE ]; then
    mv $USER_FILE ${USER_FILE}-${DATE}.bak
    echo_color green "$USER_FILE exist, rename ${USER_FILE}-${DATE}.bak"
fi
echo -e "User Password" >> $USER_FILE
echo "----------" >> $USER_FILE
for USER in user{1..10};do
    if ! id $USER &>/dev/null; then
        PASS=$(echo $RANDOM | md5sum | cut -c 1-8)
        useradd $USER
        echo $PASS | password --stdin $USER &> /dev/null
        echo -e "$USER $PASS" >> $USER_FILE
        echo "$USER User create successful"
    fi
done

4 检查软件包是否安装

#!/bin/bash
if rpm -q sysstat &> /dev/null;then
    echo "sysstat is already installed"
else 
    echo "sysstat is not installed"
fi

5 检查服务状态

#!/bin/bash
PORT_C = $(ss -anu | grep -c 123)
PS_C = $(ps -ef | grep ntpd | grep -vc grep)
if [ $PORT_C -eq 0 -o $PS_C -eq 0 ]; then
    echo "内容" | mail -s "主题"  [email protected]
fi

6 检查主机存活状态
方法1 ： 将错误的IP放到数组里面，判断是否ping失败三次

#!/bin/bash
IP_LIST = "192.168.18.1  192.168.1.1 192.168.18.2"
for IP in $IP_LIST ;do
    NUM = 1
    while [ $NUM -le 3 ]; do
        if ping -c 1 $IP > /dev/null; then
            echo "$IP ping is successful."
            break
        else 
            # echo "$IP ping is failure $NUM"
            FAIL_COUNT[$NUM]=$IP
            let NUM++
        fi
    done
    if [ ${#FAIL_COUNT[*]} -eq 3 ] ; then
        echo "${FAIL_COUNT[1]} ping is failure" 
        unset FAIL_COUNT[*]
    fi
done

方法2：将错误次数放到FAIL_COUNT变量里面判断是否ping失败三次

#!/bin/bash
IP_LIST = "192.168.18.1 192.168.1.1 192.168.28.2"
for IP in $IP_LIST ; do
    FAIL_COUNT=0
    for ((i=1;i<=3;i++));do
        if ping -c 1 $IP > /dev/null; then
            echo "$IP ping is successful"
            break
        else
            # echo "$IP ping is failure $i"
            let FAIL_ COUNT++
        fi
    done
    if [ $FAIL_COUNT -eq 3 ]; then
        echo "$IP ping is failure"
    fi
done

方法3 ：利用for循环将ping通就跳出循环继续，如果不跳出就会打印ping失败。

#!/bin/bash
ping_success_status() {
    if ping -c 1 $IP > /dev/null; then
        echo "$IP ping is successful"
        continue
    fi
}
IP_LIST = "192.168.18.1  192.168.1.1 192.168.18.2"
for IP in $IP_LIST ; do
    ping_success_status
    ping_success_status
    ping_success_status
    echo "$IP ping is failure"
done

7 监控CPU、内存和硬盘利用率
1）CPU
借助vmstat 工具来分析CPU统计信息

#!/bin/bash
DATE=$(date +%H:%M)
IP=$(ifconfig eth0 | awk -F [  : ]+ /inet addr/{print $4}) # 只支持Centos6
MAIL="[email protected]"
if ! which vmstat &> /dev/null; then
    echo "vmstat command no found , Please install procps package"
    exit 1
fi
US = $(vmstat | awk NR==3{print $13})
SY = $(vmstat | awk NR==3{print $14})
IDLE = $(vmstat | awk NR==3{print $15})
WAIT = $(vmstat | awk NR==3{print $16})
USE = $(($US+$UY))
if [ $USE -ge 50 ];then
    echo "
    Date: $DATE
    Host: $IP
    Problem: CPU utilization $USE
    "  | mail -s "CPU Monitor" $MAIL
fi

2. 内存

      #!/bin/bash
        DATE = $(date +%F""%H:%M)
        IP = $(ifconfig eth0 | awk -F [ : ]+ /inet addr/{print $4} )
        MAIL = "[email protected]"
        TOTAL = $(free -m | awk /Mem/{print $2} )
        USE = $(free -m | awk /Mem/{print $3-$6-$7} )
        FREE = $(($TOTAL-$USE))
   

   # 内存小于1G，发送报警邮件

    if [ $FREE -lt 1024 ]; then
        echo "
        Date : $DATE
        Host : $IP
        Problem : Total=$TOTAL,Use=$USE,Free=$FREE
        "  | mail -s "Memory Monitor" $MAIL
    if
   

3）硬盘

#!/bin/bash
DATE = $(date +%F" "%H:%M)
IP = $(ifconfig eth0 | awk -F [ : ]+ /inet addr/{print $4})
MAIL = "[email protected]"
TOTAL =  $(fdisk -l | awk -F [ : ]+ BEGIN{OFS="="}/^Disk /dev/{printf "%s=%sG,",$2,$3})
PART_USE = $(df -h | awk BEGIN{OFS="="}/^/dev/{print $1,int($5),$6})
for i in $PART_USE; do
    PART = $(echo $i | cut -d "=" -f1)
    USE = $(echo $i | cut -d "=" -f2)
    MOUNT = $(echo $i | cut -d "=" -f3)
    if [ $USE -gt 80 ]; then
        echo "
        Date : $DATE
        Host : $IP
        Total : $TOTAL
        Problem : $PART=$USE($MOUNT)
        "  |  mail -s "Disk Monitor" $MAIL
    fi
done

8 批量主机磁盘利用率监控
前提监控端和被监控端SSH免交互登录或者密钥登录
写一个配置文件保存被监控主机SSH连接信息，文件内容格式： IP User Port

#!/bin/bash
HOST_INFO = host.info
for IP in $(awk /^[^#]/{print $1} $HOST_INFO); do
    USER = $(awk -v ip=$IP ip==$1{print $2} $HOST_INFO)
    PORT = $(awk -v ip=$IP ip==$1{print $3} $HOST_INTO)
    TMP_FILE=/tmp/disk.tmp
    ssh -p $PORT $USER@$IP df -h > $TMP_FILE
    USE_RATE_LIST = $(awk BEGIN{OFS= "="}/^/dev/{print $1,int($5)} $TMP_FILE)
    for USE_RATE in $USE_RATE_LIST; do
         PART_NAME = ${USE_RATE%=*}
         USE_RATE = ${USE_RATE#*=}
         if [ $USE_RATE -ge 80  ]; then
             echo "Warning: $	PART_NAME Partition usage $USE_RATE%!"
         fi
     done
 done

9 检查网站可用性
1）检查URL可用性
方法1

check_url() {
    HTTP_CODE = $(curl -o /dev/null --connect-timeout 3 -s -w "%{http_code}" $1)
    if [ $HTTP_CODE -ne 200 ]; then
        echo "Warning: $1 Access failure"
    fi
    }

方法2

check_url(){
    if ! wget -T 10 --tries=1 --spider $1 >/dev/null 2>&1; then
    #-T 超时时间，--tries尝试1次，--spider爬虫模式
        echo "Warnin : $1 Access failure"
    fi
    }

2）判断三次URL可用性
方法1：利用循环技巧，如果成功就跳出当前循环，否则执行都最后一行

#!/bin/bash
check_url(){
    HTTP_CODE = $(curl -o /dev/null --connect-timeout 3 -s -w "%{http_code}" $1)
    if [ $HTTP_CODE -eq 200 ]; then
        continue
    fi
}
URL_LIST = "www.baidu.com  www.runoob.com"
for URL in $URL_LIST; do
    check_url $URL
    check_url $URL
    check_url $URL
    echo "Warning : $URL Access failure"
done

方法2：错误次数保存到变量

#!/bin/bash
URL_LIST = "www.baidu.com  www.runoob.com"
for URL in $URL_LIST; do
    FAIL_COUNT = 0
    for ((i=1;i<=3;i++)); do
        HTTP_CODE = $(curl -o /dev/null --connect-timeout 3 -s -w "%{http_code}" $URL)
        if [ $HTTP_CODE -ne 200 ]; then
            let FAIL_CONUT++
        else
            break
        fi
    done
    if [ $FAIL_COUNT -eq 3 ]; then
        echo "Warning : $URL Access failure"
    if
done

方法3：错误次数保存到数组

#!/bin/bash
URL_LIST = "www.baidu.com  www.runoob.com"
for URL in $URL_LIST ; do
    NUM = 1
    while [  $NUM -le 3 ] ; do
        HTTP_CODE= $(curl -o /dev/null --connect-timeout 3 -s -w "%{http_code}" $URL) 
        if [ $HTTP_CODE -ne 200 ]; then
            FAIL_COUNT[$NUM]=$IP #创建数组，以$NUM下标，$IP元素
            let NUM++
        else
            break
        fi
    done
    if [ ${#FAIL_COUNT[*]}  -eq 3]; then
        echo "Warning : $URL Access failure"
        unset FAIL_COUNT[*] #清空数组
    if
done

10 检查MySQL主从同步状态
#!/bin/bash
USER=bak
PASSWD=123456
IO_SQL_STATUS= $(mysql-u$USER -p$PASSWD -e show slave status/G | awk -F: /Slave_._Running/{gsub(": “,”?;print $0} ) #gsub去除冒号后面的空格
for i in $I{O}_{S}Q{L}_{S}TATUS;doTHREA{D}_{S}TATU{S}_{N}AME=${i%:}
THREAD_STATUS=KaTeX parse error: Expected '}', got '#' at position 3: {i#̲*:} if [ "THREAD_STATUS" != “Yes” ]; then
echo “Error: MySQL Master-Slave $THREAD_STATUS_NAME status is $THREAD_STATUS!”
if
done

参考：原文地址