shell: DBA需要掌握的shell知识

每个中高级DBA都需要掌握一些简单脚本的编写,这样才能从繁杂重复的基础维护工作中解脱出来,才能有时间去研究更有价值的技术。VBird在讲shell script的时候,给出了几个经典的小范例练习,对于初学shell的人来说是很好的入门,现就根据VBird给出的几个典型练习进行近一步的系统整理,总结出bash shell的系统知识,希望能给各位读者起到抛砖引玉的作用。

1.顺序执行

2.分支判断

3.循环结构

4.巩固练习

reference

1.顺序执行

练习1:用户选择输入Y/N,不区分大小写,根据用户输入屏幕打印不同内容。

考查:read,[],exit 0,&&,echo

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#!/bin/bash
#Usage: user input a charector, program shows the different result.
#Author: Alfred Zhao
#Creation: 2015-05-06
#Version: 1.0.0

#1.Input 'Y' or 'N'
read -p "Input (Y/N)>" input
[ "$input>" == "Y>" -o "$input>" == "y>" ] && echo -e "you choice is: $inputn>" && exit 0
[ "$input>" == "N>" -o "$input>" == "n>" ] && echo -e "you choice is: $inputn>" && exit 0
echo -e "I don't know what your choice is>" && exit 0

2.分支判断

两种常用的分支判断:if…else…fi分支判断,case…esac分支判断。

练习2:将练习1中的代码改写为if分支判断,使程序的执行逻辑更直观。

考查:==,||

if[]; then

elif[]; then

else

fi

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#!/bin/bash
#Usage: user input a charector, program shows the different result.
#Author: Alfred Zhao
#Creation: 2015-05-06
#Version: 1.0.1

#1.Input 'Y' or 'N'
read -p "Input (y/n)>" input
if [ "$input>" == "Y>" ] || [ "$input>" == "y>" ]; then
    echo -e "you choice is: $inputn>"
    exit 0
elif [ "$input>" == "N>" ] || [ "$input>" == "n>" ]; then
    echo -e "you choice is: $inputn>"
    exit 0
else
    echo -e "I don't know what you choice is.n>"
    exit 0
fi

练习3:用分支判断来辨别参数1的输入是否合法。

考查:$0,$1

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#!/bin/bash
#Usage: To judge $1's identity. Aha, Only Alfred is ok.
#Author: Alfred Zhao
#Creation: 2015-05-07
#Version: 1.0.0

if [ "$1>" == "Alfred>" ]; then
    echo -e "Authorization Successful! n>"
    exit 0
elif [ "$1>" == ">" ]; then
    echo -e "Waring: Authorization is null! ex> {$0 Username}n>"
    exit 0
else
    echo -e "Waring: Only Alfred can be authorized. ex> {$0 Alfred}n>"
    exit 0
fi

练习4:用case判断改写练习3.

考查:case…esac判断

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#!/bin/bash
#Usage: To judge $1's identity. Aha, Only Alfred is ok.
#Author: Alfred Zhao
#Creation: 2015-05-07
#Version: 1.0.1

case "$1>" in
    "Alfred>")
        echo -e "Authorization Successful! n>"
        ;;
    ">")
        echo -e "Waring: Authorization is null! ex> {$0 Username}n>"
        ;;
    *)
        echo -e "Waring: Only Alfred can be authorized. ex> {$0 Alfred}n>"
        ;;
esac

3.循环结构

while do done, until do done(不定循环)

练习5:输入名字直到输入的名字是“Alfred”为止。

考查:while do done

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#!/bin/bash
#Usage: Input the name until it is "Alfred>".
#Author: Alfred Zhao
#Creation: 2015-05-07
#Version: 1.0.0

while [ "$name>" != "Alfred>" ]
do
        read -p "Please Input your name: >" name
done
echo -e "nWelcome, My friend, Alfred.n>"

而如果是使用until do done,

只需要修改 while [ “$name>” != “Alfred>” ]until [ “$name>” == “Alfred>” ]

练习6:计算1+2+3+…+num的结果

考察:正则

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#!/bin/bash
#Usage: Calculate the result "1+2+...+num>".
#Author: Alfred Zhao
#Creation: 2015-05-07
#Version: 1.0.0
i=0 #i
s=0 #sum
echo -e "This program will help you calculate the result of '1+2+...+num'n>"
read -p "Please input your num: >" num
if [ "$(echo >"$num"|grep '[0-9]'|grep -v '[:alpha:]')>" == ">" ]; then
    echo -e "Waring: Please input a number.n>"
    exit 1
elif [ "$num>" -lt "1>" ]; then
    echo -e "Waring: Not support.n>"
elif [ "$num>" == "1>" ]; then
    echo -e "1=1n>"
    exit 0
elif [ "$num>" == "2>" ]; then
    echo -e "1+2=3n>"
    exit 0
elif [ "$num>" == "3>" ]; then
    echo -e "1+2+3=6n>"
    exit 0
else
    while [ "$i>" != "$num>" ]
    do
        i=$(($i+1))
        s=$(($s+$i))
    done
    echo -e "n1+2+...+$num= $sn>"
    exit 0
fi

for do done(固定循环)

for do done 第一种用法示例:

练习7:循环输出变量who的内容

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#!/bin/bash
#Usage: for do done
#Author: Alfred Zhao
#Creation: 2015-05-07
#Version: 1.0.0

for who in mum dad brother sister
do
        echo -e "This is my ${who}.n>"
done

for do done 第二种用法示例:

练习8:计算1+2+..+100的值

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#!/bin/bash
#Usage: 1+2+...+100
#Author: Alfred Zhao
#Creation: 2015-05-07
#Version: 1.0.0
sum=0
for ((i=1; i<=100; i=i+1))
do
        sum=$(($sum+$i))
done
   
echo -e "The result is $sum.n>"

4.巩固练习

1.用分支判断哪些数据库默认端口在运行.

提示:不同数据库的默认监听端口不同

Oracle数据库判断 netstat -tuln |grep “:1521 >”是否有结果;

Mysql数据库判断 netstat -tuln |grep “:3306 >”是否有结果;

IEE数据库判断 netstat -tuln |grep “:5029 >”是否有结果;

Vertica数据库判断 netstat -tuln |grep “:5433 >”是否有结果.

2.输入毕业日期,计算当前离毕业还有多少天。

提示:将时间换算成秒,相减后换算成天数。

day1=$(date –date=”20150507>” +%s)day2=$(date –date=”20160630>” +%s)days=$((($day2-$day1)/3600/24))

3.检查Linux系统所有用户的标识符与特殊参数

提示: cut -d ‘:’ -f1 /etc/passwd

4.检查192.168.1.1~192.168.1.100的主机网络情况

提示: for site in $(seq 1 100)

reference

《鸟哥的Linux私房菜》

原文:http://www.cnblogs.com/jyzhao/p/4485553.html

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