码迷，mamicode.com
首页 > 系统相关 > 详细

shell学习笔记（3）

时间：2018-03-15 23:06:13      阅读：351      评论：0      收藏：0      [点我收藏+]

标签：shell 基础 杂记

if

一、if基础

1、单分支

1.1 语法

if语句语法
    单分支结构语法：
    if [条件]; then
        指令
    fi
    或
    if  [条件]
        then
            指令
    fi

1.2 例子

[root@master4 day4]# cat if-single1.sh 
#!/bin/sh
#功能：单分支if结构整数比较，用-lt格式例子
#created by xsz
#date:20180107

if [ 10 -lt 12 ]
    then
    echo "Yes,10 is less than 12"
fi
[root@master4 day4]# sh if-single1.sh 
Yes,10 is less than 12

传参方方式：
[root@master4 day4]# cat if02.sh 
#/bin/sh
if [ $1 -lt $2 ]
    then
    echo "Year,$1 is less than $2"
fi

read接收方式：
[root@master4 day4]# cat if03.sh 
#/bin/sh
read -t 10 -p "please input two number:" num1 num2
if [ $num1 -lt $num2 ]
    then
    echo "Year,$num1 is less than $num2"
fi

以上脚本问题
1、无法完整比较整数大小
2、没有对参数的个数以及变量内容做判断

1.3 范例3

范例三（请思考）：开发脚本实现如果/server/scripts下面存在if3.sh就输出到屏幕。
注意：如果执行脚本后发现该if3.sh不存在，就自动创建这个if3.sh脚本。

我的脚本：

#!/bin/bash

i=/server/scripts/if3.sh
[ -e $i ] && cat $i && exit 0
if [ $(sh $i 2> /dev/null;echo $?) != 0 ]
    then
    echo "$i is no exist,touching if03.sh..."
    echo "I am if03.sh" > $i
fi

老男孩的脚本1：
#!/bin/sh
dir=/server/scripts
[ ! -d $dir ] && mkdir -p $dir
file="if3.sh"
if [ -f "$dir/$file" ]; then
    echo "$file is exist."
    exit 0
fi
touch $dir/$file

同学：
[root@master4 day4]# cat tiaojian.sh 
#!/bin/sh
dir=/server/scripts
file=if3.sh
cd $dir || mkdir -p $dir 
[ ! -f "$file" ] && touch $file || echo $file

1.4 内存告警脚本

开发脚本判断系统内存大小，如果低于100M就邮件报警。测试报警成功后加入系统定时任务每3分钟执行一次检查。

常见发送邮件方法：
[root@master4 day4]# mail -s "tittle" hanzhaodiba@163.com < /etc/hosts
[root@master4 day4]# echo "oldboy" | mail -s "tittle" hanzhaodiba@163.com

安装发邮件：
yum install -y sendmail

sendmail启动慢原因
1、主机名没有配置好
[root@master4 day4]# uname -n
master4.com
10.201.106.134 master4 master4.com

[root@master4 day4]# netstat -tanp | grep 25        
tcp        0      0 127.0.0.1:25            0.0.0.0:*               LISTEN      15622/sendmail

解答：重视解决问题的过程
1、先再命令行把条件取出来（我的是CentOS7）
[root@master4 day4]# free -m | grep Mem | awk ‘{print $NF}‘
122

2、编写脚本
[root@master4 day4]# vim if04.sh

#!/bin/sh

current_mem=`free -m | grep Mem | awk ‘{print $NF}‘`
mem_chars="our sys mem is:$current_mem"
if [ $current_mem -lt 200 ];then
    echo "$mem_chars" | mail -s "tittle" 635254246@qq.com
fi

[root@master4 day4]# sh -x if04.sh 
++ awk ‘{print $NF}‘
++ grep Mem
++ free -m
+ current_mem=178
+ mem_chars=‘our sys mem is:178‘
+ ‘[‘ 178 -lt 200 ‘]‘
+ mail -s tittle 635254246@qq.com
+ echo ‘our sys mem is:178‘

加入到定时任务：
[root@master4 day4]# crontab -l
#monitor memory
*/3 * * * * /bin/sh /server/scripts/day4/if04.sh > /dev/null 2>&1

2、双分支

2.1 比较两个整数大小（可用条件小写或者大于等于）

我的脚本：
[root@master4 day4]# cat if05.sh 
#!/bin/sh

if [ $1 -le $2 ];then
    if [ $1 -lt $2 ];then
    echo "$1 is less than $2"
    else
    echo "$1 is eq $2"
    fi
else
    echo "$1 is big than $2"
fi

[root@master4 day4]# cat if-double01.sh 
#!/bin/sh

if [ $1 -lt $2 ];then
    echo "$1 < $2"
else
    echo "$1 >= $2"
fi
[root@master4 day4]# sh if-double01.sh 4 5
4 < 5
[root@master4 day4]# sh if-double01.sh 2 2
2 >= 2
[root@master4 day4]# sh if-double01.sh 2 1
2 >= 1

3、多分支

3.1 还是比较两个整数大小

[root@master4 day4]# cat if-double02.sh 
#!/bin/sh

read -p "please input first number:" num1
read -p "please input second number:" num2

if [ $num1 -lt $num2 ];then
    echo "$num1 < $num2"
elif [ $num1 -gt $num2 ];then
    echo "$num1 > $num2"
else
    echo "$num1 = $num2"
fi

[root@master4 day4]# sh if-double02.sh 
please input first number:4
please input second number:3
4 > 3
[root@master4 day4]# sh if-double02.sh 
please input first number:4
please input second number:4
4 = 4
[root@master4 day4]# sh if-double02.sh 
please input first number:4
please input second number:5
4 < 5

老男孩脚本1：
[root@master4 day4]# cat if-multi01.sh 
#!/bin/sh

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

解决命令行传参，不加参数，报错问题：
[root@master4 day4]# cat judge-if-multi01-argv.sh 
#!/bin/sh
if [ $# -ne 2 ];then
    echo "$0 Usage method: num1 num2"
    exit 1
fi
if [ $1 -lt $2 ];then
    echo "$1 < $2"
elif [ $1 -eq $2 ];then
    echo "$1 = $2"
else
    echo "$1 > $2"
fi

解决输入非整数的问题：
过滤出数字：
[root@master4 day4]# echo "3434dkjfkddfd99" | sed ‘s#[a-z]##g‘
343499

反过来，过滤数字，看字段是否为0。把数字去掉，长度为0，说明是数字
[root@master4 day4]# echo "3434dkjfkddfd99" | sed ‘s#[0-9]##g‘
dkjfkddfd

[root@master4 day4]# cat judge-if-multi01-argv.sh 
#!/bin/sh
if [ $# -ne 2 ];then
    echo "$0 Usage method: num1 num2"
    exit 1
fi

[ -n "`echo $1|sed ‘s#[0-9]##g‘`" ] && {
    echo "num1 must be int."
    exit
}

[ -n "`echo $2|sed ‘s#[0-9]##g‘`" ] && {
    echo "num2 must be int."
    exit
}

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

测试：
[root@master4 day4]# sh judge-if-multi01-argv.sh nu3 34v 343
judge-if-multi01-argv.sh Usage method: num1 num2
[root@master4 day4]# sh judge-if-multi01-argv.sh nu3 34v
num1 must be int.
[root@master4 day4]# sh judge-if-multi01-argv.sh 43 34v
num2 must be int.
[root@master4 day4]# sh judge-if-multi01-argv.sh 43 3
43 > 3
[root@master4 day4]# sh judge-if-multi01-argv.sh 43 43
43 = 43
[root@master4 day4]# sh judge-if-multi01-argv.sh 43 53
43 < 53

4、判断字符串是否为数字的多种方法

4.1 sed加正则表达式

[ -n "`echo $num|sed ‘s/[0-9]//g‘`"  ] && echo "第二个参数必须为数字" && exit 1
条件表达式，大括号的用法：
[ -n "`echo $num|sed ‘s/[0-9]//‘`" ] && {
    echo "第二个参数必须为数字"
    exit 1
}

4.2 变量的子串替换加正则表达式

[root@master4 day4]# num=521old521
[root@master4 day4]# [ -z "`echo "${num//[0-9]/}"`" ] && echo 1 || echo 0
0
[root@master4 day4]# 

这个结果说明前面的结果不为1，字符串非空，即有非数字字符

————————————————

[root@master4 day4]# num=521
[root@master4 day4]# [ -z "`echo "${num//[0-9]/}"`" ] && echo 1 || echo 0
1

这个结果说明前面的结果去掉数字后为1，即没有非数字字符

4.3 变量的子串替换加正则表达式（特殊判断思路）

思路：如果num长度不为0，并且把num中的非数字部分删除，然后看结果是不是等于num本身，如果两者都成立就是数字。

[root@master4 day4]# num=123
[root@master4 day4]# [ -n "$num" -a "$num" = "${num//[^0-9]/}" ] && echo "it is num"
it is num
[root@master4 day4]# num=1d3
[root@master4 day4]# [ -n "$num" -a "$num" = "${num//[^0-9]/}" ] && echo "it is num" || echo "is not is num"
is not is num
[root@master4 day4]#

4.4 expr计算判断

把变量和整数相加看是否成功执行：

[root@master4 day4]# expr $1 + 0 > /dev/null 2>&1
[root@master4 day4]# [ $? -eq 0 ] && echo int

5、read读入方式判断整数大小

我的脚本：
#!/bin/sh
read -p "please input first num:" num1
read -p "please input second num:" num2

[ -n "`echo $num1|sed ‘s#[0-9]##g‘`" ] && {
    echo "num1 must be int."
    exit
}

[ -n "`echo $num2|sed ‘s#[0-9]##g‘`" ] && {
    echo "num2 must be int."
    exit
}

if [ $num1 -lt $num2 ];then
    echo "$num1 < $num2"
elif [ $$num1 -eq $$num2 ];then
    echo "$num1 = $num2"
else
    echo "$num1 > $num2"
fi

老男孩的脚本1：
[root@master4 day4]# vim read03.sh

#!/bin/sh

read -p "please input tow num:" a b

expr $a + 0 > /dev/null 2>&1
RETVAL1=$?
expr $b + 0 > /dev/null 2>&1
RETVAL2=$?

[ "$RETVAL1" -eq 0 -a $RETVAL2 -eq 0 ] || {
    echo "argv1 and argv2 must be int."
    exit 2
}

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

二、MySQL监控

1、方法一

1.1 监听端口

我的脚本1：
[root@master4 MySQL]# cat 01.sh 
#!/bin/bash
# pang duan mysqld starting

if [ "`netstat -tan | grep 3306 | awk ‘{print $6}‘ | head -1`" == "LISTEN" ]; then
    echo "mysqld is starting"
else
    echo "mysqld is stop.Now is starting mysqld service..."
    systemctl start mysqld.service
    pid=$(lsof -i:3306 | head -2 | grep mysqld | awk ‘{print $2}‘)
    echo "staring mysqld ok,the mysqld PID is $pid"  
fi

我的脚本2：
[root@master4 MySQL]# cat 02.sh 
#!/bin/bash
# pang duan mysqld starting

if [ "`systemctl status mysqld.service | grep Active | awk ‘{print $2}‘`" == "active" ]; then
    echo "mysqld is starting"
else
    echo "mysqld is stop.Now is starting mysqld service..."
    systemctl start mysqld.service
    pid=$(lsof -i:3306 | head -2 | grep mysqld | awk ‘{print $2}‘)
    echo "staring mysqld ok,the mysqld PID is $pid"  
fi
[root@master4 MySQL]# 

老男孩的脚本1（这个方法有问题，进程被杀死，取得值为空，会报错）：
[root@master4 MySQL]# cat judgedb_by_port01.sh 
#!/bin/sh

port=`netstat -lnt | grep 3306 | awk -F ‘[ :]+‘ ‘{print $5}‘`
if [ $port -ne 3306 ];then
    echo "mysql is stoped"
    systemctl start mysqld
fi

老男孩的脚本1【改进版】（取netstat显示的行数）：
[root@master4 MySQL]# cat judgedb_by_port01.sh 
#!/bin/sh

portnum=`netstat -lnt | grep 3306 | wc -l`
if [ $portnum -ne 1 ];then
    echo "mysql is stoped"
    systemctl start mysqld
else
    echo "mysql is running"
fi

测试：
[root@master4 MySQL]# sh judgedb_by_port01.sh 
mysql is stoped
[root@master4 MySQL]# sh judgedb_by_port01.sh 
mysql is running
[root@master4 MySQL]#

2、方法二

2.0 监控端口和进程

我的脚本1：
[root@master4 MySQL]# cat judgedb_by_port01.sh 
#!/bin/sh

portnum=`netstat -lnt | grep 3306 | wc -l`
pid=`ps -ed | grep mysqld | wc -l`
if [ $portnum -ne 1 -o $pid -le 1 ];then
    echo "mysql is stoped"
    systemctl start mysqld
else
    echo "mysql is running"
fi

[root@master4 MySQL]# bash -x judgedb_by_port01.sh 
++ wc -l
++ netstat -lnt
++ grep 3306
+ portnum=0
++ grep mysqld
++ wc -l
++ ps -ed
+ pid=0
+ ‘[‘ 0 -ne 1 -a 0 -le 1 ‘]‘
+ echo ‘mysql is stoped‘
mysql is stoped
+ systemctl start mysqld

老男孩的脚本1：
[root@master4 MySQL]# cat judgedb_by_port02.sh 
#!/bin/sh

portnum=`netstat -lnt | grep 3306 | wc -l`
processsum=`ps -ef | grep mysql | grep -v grep | wc -l`
if [[ $portnum -eq 1 || $processsum -eq 2 ]];then
    echo "mysql is running"
else
    echo "mysql is stoped"
    echo "Staring MySQL..."
    systemctl start mysqld
fi

测试：
[root@master4 MySQL]# sh -x judgedb_by_port02.sh 
++ wc -l
++ netstat -lnt
++ grep 3306
+ portnum=0
++ grep -v grep
++ wc -l
++ ps -ef
++ grep mysql
+ processsum=0
+ [[ 0 -eq 1 ]]
+ [[ 0 -eq 2 ]]
+ echo ‘mysql is stoped‘
mysql is stoped
+ systemctl start mysqld
[root@master4 MySQL]# 
[root@master4 MySQL]# 
[root@master4 MySQL]# sh -x judgedb_by_port02.sh 
++ wc -l
++ netstat -lnt
++ grep 3306
+ portnum=1
++ grep mysql
++ grep -v grep
++ ps -ef
++ wc -l
+ processsum=2
+ [[ 1 -eq 1 ]]
+ echo ‘mysql is running‘
mysql is running
[root@master4 MySQL]# 

老男孩脚本2:
[root@master4 MySQL]# cat judgedb_by_port03.sh 
#!/bin/bash
#function:check mysql status

MySQLSTARTUP="systemctl start mysqld.service"
DbProcessCount=`ps -ef | grep mysql | grep -v brep | wc -l`
DbPortCount=`netstat -lnt | grep 3306 | wc -l`
if [ $DbProcessCount -eq 2 ] && [ $DbPortCount -eq 1 ];then
    echo "MySQL is running"
else
    $MySQLSTARTUP > /tmp/mysql.log
    sleep 10;
    DbProcessCount=`ps -ef | grep mysql | grep -v grep | wc -l`
    DbPortCount=`netstat -lnt | grep 3306 | wc -l`
    if [ $DbProcessCount -ne 2 ] || [ $DbPortCount -ne 1 ];then
    pkill mysqld > /dev/null 2>&1
    sleep 5
    pkill mysqld > /dev/null 2>&1
    sleep 5
    [ $DbProcessCount -eq 0 ] && MySQLSTARTUP >> /tmp/mysql.log
    [ $? -eq 0 ] && echo "mysql is started"
    fi

    mail -s "mysql restarted" xxxxxx@qq.com < /tmp/mysql.log
fi

2.2 转化脚本格式为UNIX模式

[root@master4 MySQL]# dos2unix judgedb_by_port03.sh 
dos2unix: converting file judgedb_by_port03.sh to Unix format ...

3、方法三

3.0 脚本测试连接

我的脚本1：
[root@master4 MySQL]# cat 03.sh 
#!/bin/sh

value=`mysql -uroot -p‘root‘ -S /var/lib/mysql/mysql.sock -e "SELECT VERSION();" > /dev/null 2>&1;echo $?`
portnum=`netstat -lnt | grep 3306 | wc -l`
processsum=`ps -ef | grep mysql | grep -v grep | wc -l`
if [[ $portnum -eq 1 && $processsum -eq 2 && value -eq 0 ]];then
    echo "mysql is running"
else
    echo "mysql is stoped"
    echo "Staring MySQL..."
    systemctl start mysqld
    Version=`mysql -uroot -p‘root‘ -S /var/lib/mysql/mysql.sock -e "SELECT VERSION();" | grep -v "()"`
    echo "The MySQL version is $Version"
fi

老男孩的脚本1：
[root@master4 MySQL]# cp judgedb_by_port02.sh judgedb_by_mysql04.sh

[root@master4 MySQL]# cat judgedb_by_mysql04.sh
#!/bin/sh
mysql -uroot -proot -S /var/lib/mysql/mysql.sock -e "SELECT VERSION();" >/dev/null 2>&1
if [[ $? -eq 0 ]];then
    echo "mysql is running"
else
    echo "mysql is stoped"
    echo "Staring MySQL..."
    systemctl start mysqld
fi

异地连接，使用-h IP

4、方法四

4.1 通过php/java程序监控MySQL

三、监控nginx或apache

1、

1.1 查看nginx是否运行

[root@master4 ~]# netstat -tan | grep 80
tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN     
tcp6       0      0 :::80                   :::*                    LISTEN     
[root@master4 ~]# lsof -i :80

[root@master4 ~]# ps -ef | grep nginx

[root@node3 ~]# curl -I 10.201.106.134

[root@node3 ~]# wget 10.201.106.134

[root@node3 ~]# curl -o /dev/null -s -w "%{http_code}" 10.201.106.134
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100  3700  100  3700    0     0   695k      0 --:--:-- --:--:-- --:--:--     0

curl -s  静默显示

[root@node3 ~]# nmap 10.201.106.134 -p 80 | grep open | wc -l
1

[root@node3 ~]# curl -o /dev/null -s -w %{http_code} http://10.201.106.134
200[root@node3 ~]# 

[root@node3 ~]# curl -s -I http://10.201.106.134 | sed -n ‘1p‘ | cut -d " " -f2
200

1.2 namp判断nginx是否启动

[root@master4 nginx]# vim judgeweb_by_port01.sh 

#!/bin/sh

portnum=`nmap 10.201.106.134 -p 80 | grep open | wc -l`
if [ $portnum -ne 1 ];then
    echo "nginx is stoped"
    systemctl start nginx
else
    echo "nginx is running"
fi

1.3 wget

[root@master4 nginx]# vim judgeweb_by_wget-url02.sh 

#!/bin/sh

wget -T 15 -q --spider http://10.201.106.134
if [ $? -ne 0 ];then
    echo "nginx is stoped"
    systemctl start nginx
else
    echo "nginx is running"
fi

1.4 获取状态码判断

[root@master4 nginx]# vim judgeweb_by_curl-code03.sh 

#!/bin/sh

httpcode=`curl -o /dev/null -s -w %{http_code} http://10.201.106.134`
if [ "$httpcode" != "200" ];then
    echo "nginx is stoped"
    systemctl start nginx 
else
    echo "nginx is running"
fi

[root@master4 nginx]# pkill nginx
[root@master4 nginx]# sh judgeweb_by_curl-code03.sh 
nginx is stoped
[root@master4 nginx]# sh judgeweb_by_curl-code03.sh 
nginx is running
[root@master4 nginx]#

shell学习笔记（3）

标签：shell 基础 杂记

原文地址：http://blog.51cto.com/zhongle21/2087365
踩
(0)
赞
(0)
   
举报
评论 一句话评论（0）
登录后才能评论！
分享档案
更多>
2021年07月29日 (22)
2021年07月28日 (40)
2021年07月27日 (32)
2021年07月26日 (79)
2021年07月23日 (29)
2021年07月22日 (30)
2021年07月21日 (42)
2021年07月20日 (16)
2021年07月19日 (90)
2021年07月16日 (35)
周排行
mamicode.com排行更多图片
更多
友情链接
兰亭集智   国之画   百度统计   站长统计   阿里云   chrome插件   新版天听网
关于我们 - 联系我们 - 留言反馈
© 2014 mamicode.com 版权所有  联系我们:gaon5@hotmail.com
迷上了代码！