Shell脚本的语句
一 条件测试操作
1,1 test命令
测试表达式是否成立,若成立返回0,否则返回其它数值
格式1:test 条件表达式
格式2:[ 条件表达式 ] (至少应有一个空格)
例如:
[[email protected] ~]# touch aa
[[email protected] ~]# ls -lh
[[email protected] ~]# test -f aa
[[email protected] ~]# echo $?
0 返回0表示条件成立
[[email protected] ~]# test -d aa
[[email protected] ~]# echo $?
1 返回1表示条件不成立
[[email protected] ~]# [ -f aa ]
[[email protected] ~]# echo $?
0
1.2 文件测试
[ 操作符 文件或目录 ]
1.2.1 常用的测试操作符
-d :测试是否为目录(Directory)
-e :测试目录或文件是否存在(Exist)
-f : 测试是否为文件(File)
-r : 测试当前用户是否有权限读取(Read)
-w :测试当前用户是否有权限写入 (Write)
-x :测试当前用户是否有权限执行 (eXcute)
例如:
[[email protected] ~]# [ -d aa ]
[[email protected] ~]# echo $?
1
[[email protected] ~]# [ -e aa ]
[[email protected] ~]# echo $?
0
[[email protected] ~]# [ -r aa ]
[[email protected] ~]# echo $?
0
[[email protected] ~]# [ -w aa ]
[[email protected] ~]# echo $?
0
[[email protected] ~]# [ -x aa ]
[[email protected] ~]# echo $?
&&:逻辑与,而且意思(做一个条件判断,前面条件成立,才会输出;不成立,就不输出)
[[email protected] ~]# [ -x aa ] && echo "this file has x permission"
[[email protected] ~]# chmod +x aa
[[email protected] ~]# [ -x aa ] && echo "this file has x permission"
this file has x permission
[[email protected] ~]# chmod -x aa
[[email protected] ~]# [ -x aa ] || echo "this file has x permission"
this file has x permission
||:或,一个条件成立即可
1.3 整数值比较
[ 整数1 操作符 整数2 ]
条件判断的前提条件,必须是整数
1.3.1 常用的测试操作符
-eq:等于(Equal)
-ne :不等于 (Not Equal)
-gt:大于 (Greater Than)
-lt:小于(Lesser Than)
-le:小于或等于 (Lesser or Equal)
-ge:大于或等于 (Greater or Equal)
循环条件:20次
i=0 i<=19或i<20
i=1 i<=20或i<21
例如:
[[email protected] ~]# who
[[email protected] ~]# who | wc -l 条件判断先取值
5
[[email protected] ~]# [ $(who | wc -l) -ge 4 ] && echo "too many."
too many. 用户数大于等于4
[[email protected] ~]# [ $(who | wc -l) -lt 4 ] && echo "too many."
[[email protected] ~]# free -m 可用内存容量
total used free shared buff/cache available 可用
Mem: 1823 1229 80 13 513 347
Swap: 3071 28 3043
[[email protected] ~]# free -m | grep Mem:
Mem: 1823 1229 80 13 513 347
[[email protected] ~]# free -m | grep Mem: | awk '{print $7}' 做哪个字段的输出第7位
347
[[email protected] ~]# echo $(free -m | grep Mem: | awk '{print $7}') 首先保证可以输出
346
[[email protected] ~]# [ $(free -m | grep Mem: | awk '{print $7}') -le 1024 ] && echo "内存可用空间:$(free -m | grep Mem: | awk '{print $7}') MB" 内存可用空间是否小于等于1024MB
内存可用空间:346 MB
1.4 字符串比较:
格式1:[ 字符串1 = 字符串2 ]
[ 字符串1 != 字符串2 ]
格式2:[ -z 字符串 ]
1.4.1 常用的测试操作符
=:字符串内容相同
!=:字符串内容不同,!号表示相反的意思
-z:字符串内容为空
例如:
[[email protected] ~]# [ 'b' = 'c' ]
[[email protected] ~]# echo $?
1
[[email protected] ~]# [ 'b' = 'c' ] && echo "b不等于c"
[[email protected] ~]# [ 'b' != 'c' ] && echo "b不等于c"
b不等于c
[[email protected] ~]# [ -z '' ] && echo "空的"
空的
[[email protected] ~]# read -p "是否覆盖现有内容?(yes/no)" ack
是否覆盖现有内容?(yes/no)yes
[[email protected] ~]# [ $ack = "yes" ] && echo "覆盖"
覆盖
[[email protected] ~]#
[[email protected] ~]# [ $ack = "no" ] && echo "不覆盖"
[[email protected] ~]# read -p "是否覆盖现有内容?(yes/no)" ack
是否覆盖现有内容?(yes/no)no
[[email protected] ~]# [ $ack = "no" ] && echo "不覆盖"
不覆盖
1.5 逻辑测试
格式1:[ 表达式1 ] 操作符 [ 表达式2 ] ...
格式2:命令1 操作符 命令2 ....
1.5.1 常用的测试操作符
-a或&&:逻辑与,“而且”的意思
-o或||:逻辑或,“或者”的意思
!:逻辑否
二 if语句
2.1 单分支结构 (单一情况)
if 条件测试操作 if 已用磁盘空间>80%
then 命令序列 then 报警
fi fi
在这里插入图片描述
例如:
1.针对目录模拟
[[email protected] ~]# vi mkdir.sh
[[email protected] ~]# chmod +x mkdir.sh
[[email protected] ~]# ./mkdir.sh
[[email protected] ~]# ls -R /a
[[email protected] ~]# cd /
[[email protected] /]# ls -lh
#!/bin/bash 查看目录是否存在,不存在就创建目录
# 创建目录
dir="/a/b" 做判断是否存在
if [ ! -d $dir ]
then mkdir -p $dir
fi
2.针对用户模拟
[[email protected] ~]# echo $USER
root
[[email protected] ~]# su zjq
[[email protected] root]$ sudo vi a.sh
[[email protected] root]$ sudo chmod +x a.sh
[[email protected] root]$ sudo ./a/sh
#!/bin/bash
# 判断当前用户是否为root 查看当前用户是否是root,不是报错
if [ ! “$USER” = “root” ]
then echo "当前用户不是root"
fi
2.2 双分支结构(正反两种情况)
if 条件测试操作 if 80端口是否在监听
then 命令序列1 then 网站服务已在运行
else 命令序列2 else 启动httpd服务
fi fi
1.查看80端口是否开启
[[email protected] ~]# netstat -anpt | grep 80
tcp 0 0 20.0.0.11:22 20.0.0.1:50080 ESTABLISHED 61372/sshd: [email protected]
[[email protected] ~]# echo $?
0
[[email protected] ~]# vi s1.sh
[[email protected] ~]# chmod +x s1.sh
[[email protected] ~]# ./s1.sh
#!/bin/bash
# 判断apache是否启动中
netstat -anpt | grep 80
if [ $? = 0 ]
then echo "网络服务正在运行"
else echo "网站服务停止"
fi
2.地址通信查看
[[email protected] ~]# ping 20.0.0.10
[[email protected] ~]# echo $?
0
[[email protected] ~]# ping 20.0.0.15
[[email protected] ~]# echo $?
[[email protected] ~]# vi ping.sh
[[email protected] ~]# chmod +x ping.sh
[[email protected] ~]# ./ping.sh 20.0.0.10
20.0.0.10 is up.
[[email protected] ~]# ./ping.sh 20.0.0.15
20.0.0.15 is down.
#!/bin/bash
ping -c 3 $1 &> /dev/null
if [ $? = 0 ]
then echo "$1 is up."
else echo "$1 is down."
fi
3.天气好坏分类
[[email protected] ~]# vi tianqi.sh
[[email protected] ~]# chmod +x tianqi.sh
[[email protected] ~]# ./tianqi.sh
天气天晴
好天气
[[email protected] ~]# ./tianqi.sh
天气阴天
今天可能需要带伞
#!/bin/bash
# 天气
read -p "天气" weather
if [ "$weather" = "天晴" ]
then echo "好天气"
else echo "今天可能需要带伞"
fi
2.3 多分支结构
if 条件测试操作1 if 分数为85-100之间
then 命令序列1 then 判为优秀
elif 条件测试操作2 elif的 分数为70-84之间
then 命令序列2 then 发 then 判为合格
else esle
命令序列3 判为不合格
fi fi
1.成绩查询
[[email protected] ~]# vi grade.sh
[[email protected] ~]# chmod +x grade.sh
[[email protected] ~]# ./grade.sh
#!/bin/bash
# 成绩判断
read -p "您的成绩为:" grade
if [ $grade -gt 100 ] || [ $grade -lt 0 ]
then echo "输入错误,请重新输入0-100之间的数值"
elif [ $grade -ge 85 ] && [ $grade -le 100 ]
then echo "优秀!!!"
elif [ $grade -ge 70 ] && [ $grade -le 84 ]
then echo "良好!!!"
elif [ $grade -ge 60 ] && [ $grade -le 69 ]
then echo "合格!!!"
else echo "不合格!!!"
fi
2.3.1提取性能监控指标项目(磁盘占用,CPU使用,内存使用)
1,磁盘占用情况
[[email protected] ~]# df -Th
[[email protected] ~]# df -Th | grep "/$"
[[email protected] ~]# df -Th | grep "/$" | awk '{print $6}'
[[email protected] ~]# df -Th | grep "/$" | awk '{print $6}' | awk -F% '{print $1}'
[[email protected] ~]# disk=$( df -Th | grep "/$" | awk '{print $6}' | awk -F% '{print $1}')
[[email protected] ~]# [ $disk -gt 10 ] && echo "too less."
[[email protected] ~]# [ $disk -lt 10 ] && echo "too less."
2,内存占用情况
[[email protected] ~]# free
[[email protected] ~]# free | grep "Mem:" | awk '{print $3}'
[[email protected] ~]# free | grep "Mem:" | awk '{print $2}'
[[email protected] ~]# expr $(free | grep "Mem:" | awk '{print $3}') / $(free | grep "Mem:" | awk '{print $2}')
[[email protected] ~]# expr $(free | grep "Mem:" | awk '{print $3}') \* 100 / $(free | grep "Mem:" | awk '{print $2}')
[[email protected] ~]# echo $(expr $(free | grep "Mem:" | awk '{print $3}') \* 100 / $(free | grep "Mem:" | awk '{print $2}'))
[[email protected] ~]# mem=$(expr $(free | grep "Mem:" | awk '{print $3}') \* 100 / $(free | grep "Mem:" | awk '{print $2}'))
3,CPU占用率
[[email protected] ~]# mpstat
[[email protected] ~]# mpstat | tail -1 | awk '{print $12}'
[[email protected] ~]# mpstat | tail -1 | awk '{print $12}' | awk -F. '{print $1}'
[[email protected] ~]# expr 100 - $( mpstat | tail -1 | awk '{print $12}' | awk -F. '{print $1}')
4.准备配置数据
disk=$( df -Th | grep "/$" | awk '{print $6}' | awk -F% '{print $1}')
mem=$(expr $(free | grep "Mem:" | awk '{print $3}') \* 100 / $(free | grep "Mem:" | awk '{print $2}'))
cpu=$(expr 100 - $( mpstat | tail -1 | awk '{print $12}' | awk -F. '{print $1}'))
if [ $disk -ge 85 ] then echo "磁盘占有率超过85%"
if [ $mem -ge 90 ] then echo "内存占有率超过90%"
if [ $cpu -ge 90 ] then echo "cpu占有率超过90%"
5.发送报警邮件
[[email protected] ~]# rpm -qa mailx 查看是否安装程序
[[email protected] ~]# vi /etc/mail.rc 配置文件
[[email protected] ~]# echo "123456" | mail -s "test" [email protected]
发送邮件,内容:123456
set [email protected] 发送邮箱地址
set smtp=smtp.qq.com 邮箱使用的smtp服务器的域名
set [email protected] smtp邮件发送时登录的账号
set smtp-auth-password=........ 授权码
set smtp-auth=login smtp的状态,登录状态
6.查看是否可以上网,发送邮件
登录邮箱查看邮件
7.进行报警文件测试
[[email protected] ~]# vim alert.sh
[[email protected] ~]# chmod +x alert.sh
[[email protected] ~]# ./alert.sh
1 #!/bin/bash
2 # 硬件巡检,对cpu,内存,磁盘超过阀值报警
3 disk=$( df -Th | grep "/$" | awk '{print $6}' | awk -F% '{print $1}')
4 mem=$(expr $(free | grep "Mem:" | awk '{print $3}') \* 100 / $(free | grep "Mem:" | awk '{print $2}'))
5 cpu=$(expr 100 - $( mpstat | tail -1 | awk '{print $12}' | awk -F. '{print $1}'))
6 alert_file=/root/alert.txt
7 [email protected]
8 if [ $disk -ge 10 ]
9 then echo "磁盘占有率超过85%" >> $alert_file
10 fi
11 if [ $mem -ge 5 ]
12 then echo "内存占有率超过90%" >> $alert_file
13 fi
14 if [ $cpu -ge 2 ]
15 then echo "cpu占有率超过90%" >> $alert_file
16 fi
17 if [ -f $alert_file ]
18 then
19 cat $alert_file | mail -s "alert report" $mailbox
20 rm -rf $alert_file
21 fi
进入邮箱看出报警信息
三 case语句结构
3.1 case多分支结构
case 变量值 in case 分数 in
模式1) 85-100)
命令序列1 判为优秀
;; ; ;
模式2) 70-84)
命令序列2 判为合格
; ; ; ;
.... ......
*) *)
默认命令序列 判为不合格
esac esac
3.2 case语句应用示例
case多分支语句
[email protected] #cathitkey.sh
#!/bin/bash
read -p "请输入-个字符,并按Enter键确认:" KEY
case "$KEY" in
[a-z][A-Z]) 匹配任意字母
echo "您输入的是字母."
;;
[0-9]) 匹配任意数字
echo "您输入的是数字."
;;
*) 匹配任意字符
echo "您输入的是空格、功能键或其他控制字符. "
esac
例如:
[[email protected] ~]# vi case.sh
[[email protected] ~]# chmod +x case.sh
[[email protected] ~]# ./case.sh
#!/bin/bash
# 判断输入的字符是哪种类型
read -p "请输入一个字符并按enter回车确认" key
case "$key" in
[a-z]|[A-Z]) 匹配任意字母
echo "您输入的是字母."
;;
[0-9]) 匹配任意数字
echo "您输入的是数字."
;;
*) 匹配任意字符
echo "您输入的是空格,功能键,其它控制字符."
exit 1
esac
成绩分类判断
[[email protected] ~]# vi case2.sh
[[email protected] ~]# chmod +x case2.sh
[[email protected] ~]# ./case2.sh
#!/bin/bash
# 成绩输入判断
read -p "成绩:" b
case "$b" in
100)
echo "满分"
;;
9[0-9])
echo "优秀"
;;
8[0-9])
echo "良"
;;
7[0-9])
echo "良好"
;;
6[0-9])
echo "合格"
;;
*)
echo "不及格"
esac