| 导读 | Shell是一个命令行解释器，它为用户提供了一个向内核发送请求以便运行程序的界面系统级程序，用户可以用Shell来启动、挂起、停止甚至是编写一些程序。简单来讲，Shell是连接用户与内核的桥梁，是用户与内核交流的工具。 |
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）有两个命令能帮助我调试脚本：set -e 遇到执行非0时退出脚本，set-x 打印执行过程。
6）写脚本一定先测试再到生产上。
1 获取随机字符串或数字
获取随机8位字符串：
class="">方法1：# echo $RANDOM |md5sum |cut -c 1-8471b94f2方法2：# openssl rand -base64 4vg3BEg==方法3：# cat /proc/sys/kernel/random/uuid |cut -c 1-8ed9e032c
获取随机8位数字：
class="">方法1：# echo $RANDOM |cksum |cut -c 1-823648321方法2：# openssl rand -base64 4 |cksum |cut -c 1-838571131方法3：# date +%N |cut -c 1-869024815
cksum：打印CRC效验和统计字节
2 定义一个颜色输出字符串函数
class="">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[31;40m$2\033[0m" fi}方法2：function echo_color() { case $1 in green) echo -e "\033[32;40m$2\033[0m" ;; red) echo -e "\033[31;40m$2\033[0m" ;; *) echo "Example: echo_color red string" esac}使用方法：echo_color green "test" function关键字定义一个函数，可加或不加。
3 批量创建用户
class="">#!/bin/bashDATE=$(date +%F_%T)USER_FILE=user.txtecho_color(){ if [ $1 == "green" ]; then echo -e "\033[32;40m$2\033[0m" elif [ $1 == "red" ]; then echo -e "\033[31;40m$2\033[0m" fi}# 如果用户文件存在并且大小大于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"fiecho -e "User\tPassword" >> $USER_FILEecho "----------------" >> $USER_FILEfor USER in user{1..10}; do if ! id $USER &>/dev/null; then PASS=$(echo $RANDOM |md5sum |cut -c 1-8) useradd $USER echo $PASS |passwd --stdin $USER &>/dev/null echo -e "$USER\t$PASS" >> $USER_FILE echo "$USER User create successful." else echo_color red "$USER User already exists!" fidone 4 检查软件包是否安装
class="">#!/bin/bashif rpm -q sysstat &>/dev/null; then echo "sysstat is already installed."else echo "sysstat is not installed!"fi
5 检查服务状态
class="">#!/bin/bashPORT_C=$(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" dst@example.comfi
6 检查主机存活状态
方法1：将错误IP放到数组里面判断是否ping失败三次
class="">#!/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[*] fidone 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
class="">#!/bin/bash IP_LIST="192.168.18.1 192.168.1.1 192.168.18.2"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!" fidone
方法3：利用for循环将ping通就跳出循环继续，如果不跳出就会走到打印ping失败
class="">#!/bin/bashping_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。class="">#!/bin/bashDATE=$(date +%F" "%H:%M)IP=$(ifconfig eth0 |awk -F '[ :]+' '/inet addr/{print $4}') # 只支持6MAIL="example@mail.com"if ! which vmstat &>/dev/null; then echo "vmstat command no found, Please install procps package." exit 1fiUS=$(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 $16}')USE=$(($US+$SY))if [ $USE -ge 50 ]; then echo " Date: $DATE Host: $IP Problem: CPU utilization $USE " | mail -s "CPU Monitor" $MAILfi 2）内存
class="">#!/bin/bashDATE=$(date +%F" "%H:%M)IP=$(ifconfig eth0 |awk -F '[ :]+' '/inet addr/{print $4}') MAIL="example@mail.com"TOTAL=$(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" $MAILfi 3）硬盘
class="">#!/bin/bashDATE=$(date +%F" "%H:%M)IP=$(ifconfig eth0 |awk -F '[ :]+' '/inet addr/{print $4}') MAIL="example@mail.com"TOTAL=$(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 fidone> 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
class="">#!/bin/bashHOST_INFO=host.infofor 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_INFO) 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 $USE_RATE%!" fi donedone 9 检查网站可用性
1）检查URL可用性
class="">方法1：check_url() { HTTP_CODE=$(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 "Warning: $1 Access failure!" fi} 使用方法：check_url www.baidu.com
2）判断三次URL可用性 思路与上面检查主机存活状态一样。class="">方法1：利用循环技巧，如果成功就跳出当前循环，否则执行到最后一行#!/bin/bash check_url() { HTTP_CODE=$(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.agasgf.com"for URL in $URL_LIST; do check_url $URL check_url $URL check_url $URL echo "Warning: $URL Access failure!"done class="">方法2：错误次数保存到变量#!/bin/bash URL_LIST="www.baidu.com www.agasgf.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_COUNT++ else break fi done if [ $FAIL_COUNT -eq 3 ]; then echo "Warning: $URL Access failure!" fidone class="">方法3：错误次数保存到数组#!/bin/bash URL_LIST="www.baidu.com www.agasgf.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: $URL Access failure!" unset FAIL_COUNT[*] #清空数组 fidone 10 检查MySQL主从同步状态
class="">#!/bin/bash USER=bakPASSWD=123456IO_SQL_STATUS=$(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 $IO_SQL_STATUS; do THREAD_STATUS_NAME=${i%:*} THREAD_STATUS=${i#*:} if [ "$THREAD_STATUS" != "Yes" ]; then echo "Error: MySQL Master-Slave $THREAD_STATUS_NAME status is $THREAD_STATUS!" fidone 本章写的Shell脚本例子都比较实用，在面试题中也经常出现，希望大家参考着多动手写写，不要复制粘贴就拿来跑，这样是学不会的！
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