以练代学之shell入门(一)

时间：2023-03-08 17:40:27

5年前的时候，开始接触linux操作系统，接触的第一步就是学习shell脚本。用小脚本以连代学入了门。

1) 9*9乘法输出

2) 检验主机的服务是否启动

3) 冒泡排序

4) 备份当时team服务器上的dokuwili、mantis等应用。

 

一、 9*9乘法输出

主要目的是练习变量、for循环语句、if条件语句。

功能是输出9*9乘法

稚嫩的手法：

#!/bin/bash

#Function:output 9*9 expression

#Date:2011 04 21

#Version:1.0.0.0

LANG=C

export LANG

i=1

j=1

rst=0

for i in $(seq 1 9)

do

    result=''

    for j in $(seq 1 $i)

    do

        rst=$(($i*$j))

        result="$result$i*$j=$rst "

        j=$(($j+1))

    done

echo $result

i=$(($i+1))

done

exit 0

效果

[root@Grace ~]# ./99Plus.sh

1*1=1

2*1=2 2*2=4

3*1=3 3*2=6 3*3=9

4*1=4 4*2=8 4*3=12 4*4=16

5*1=5 5*2=10 5*3=15 5*4=20 5*5=25

6*1=6 6*2=12 6*3=18 6*4=24 6*5=30 6*6=36

7*1=7 7*2=14 7*3=21 7*4=28 7*5=35 7*6=42 7*7=49

8*1=8 8*2=16 8*3=24 8*4=32 8*5=40 8*6=48 8*7=56 8*8=64

9*1=9 9*2=18 9*3=27 9*4=36 9*5=45 9*6=54 9*7=63 9*8=72 9*9=81

二、 检验主机的服务是否启动

主要目的是if条件语句、``。

功能是检验主机服务是否启动，并输出对应的信息

稚嫩的手法：

#!/bin/bash

#Function:using "if then" to show host's service.

#Date:2011 04 21

#Version:1.0.0.0

#1.print the program's function

echo "Now,the service of your linux system will be detected!"

echo "the www,ftp,ssh and send mail+pop3 will be detected!"

echo " "

#2.www

  www=`netstat -an|grep LISTEN|grep :80`

if [ "$www" != "" ]; then

    echo "WWW is running"

else

    echo "WWW is NOT running"

fi

#3.ftp

  ftp=`netstat -an|grep LISTEN|grep :21`

if [ "$ftp" != "" ]; then

    echo "FTP is running"

else

    echo "FTP is NOT running"

fi

#4.ssh

  ssh=`netstat -an|grep LISTEN|grep :22`

if [ "$ssh" != "" ]; then

    echo "SSH is running"

else

    echo "SSH is NOT running"

fi

#5.smtp+pop3

smtp=`netstat -an|grep LISTEN|grep :25`

pop3=`netstat -an|grep LISTEN|grep :110`

if [ "$smtp" != "" ] && [ "$pop3" != "" ]; then

    echo "sendmail is OK!"

elif [ "$smtp" != "" ] && [ "$pop3" == "" ]; then

    echo "sendmail have some proplems of your pop3!"

elif [ "$smtp" == ""] && [ "$pop3" != "" ]; then

    echo "sendmail have some proplems of your SMTP!"

else

    echo "sendmail is not running!"

fi

效果

[root@Grace ~]# ./port-test.sh

Now,the service of your linux system will be detected!

the www,ftp,ssh and send mail+pop3 will be detected!

 
WWW is NOT running

FTP is NOT running

SSH is running

sendmail have some proplems of your pop3!

三、 冒泡排序

练习参数的使用、eval、if条件语句、比较符号、for循环语句。

功能是一次性输入n个数字，请按降序输出

拙劣的手法：

#Function:asc sort

#Date:2011 04 19

#Version:1.0.0.0

LANG=C

export LANG

#1.read numbers

i=$#

var[1]=0

for (( a=1; a<=$i; a=a+1 ))

do

    eval var[$a]=\$$a

done

#2.sort

num=""

for (( a=1; a<=$i-1; a=a+1 ))

do

    for (( j=1; j<=$i-$a; j=j+1 ))

    do

        if [ "${var[$j]}" -gt "${var[$j+1]}" ]; then

            num="${var[$j]}"

            var[$j]="${var[$j+1]}"

            var[$j+1]="$num"

        fi

    done

done

#3.output

result=""

for (( a=1;a<=$i-1; a=a+1 ))

do

    result="$result${var[$a]},"

done

echo "$result${var[$i]}"

exit 0

效果

[root@Grace ~]# ./asort.sh 8 100 9 2 0 119 19

0,2,8,9,19,100,119

[root@Grace ~]# ./asort.sh 3220 456 1000 9 0 2 10 20 98 166

0,2,9,10,20,98,456,1000,3220,32200

显而易见的缺点是：

没有对输入进行校验。

此外，获取值也可以使用read读取

四、 备份服务器的应用组件

主要目的是练习case语句、同时真的需要备份数据。

功能是

1) 备份目录 'data' 到 'qvbackp'

2) 加入简单的输入校验

3) 输出备份信息

4) 备份成功的话，同时把恢复脚本写好

拙劣的手法：

#!/bin/bash

#Function:backup directory 'data' to dest 'qvbackp'

#Date:2011 04 25

#Version:1.0.0.0

  declare -i count=$#

# step1:backup and move backuped files to another directory

  case $count in

    "1")

        if [ "$1" == "--help" ] ; then

            echo "Usage: qvbackup.sh    SOURCE-DIRECTORY    DEST-DIRECTORY"

            echo "Backup files of SOURCE-DIRECTORY to DEST-DIRECTORY."

            exit

         else

            echo "Invalid parameters, make sure all parameters are correct. "

            exit

         fi

    ;;

    "2")

        if [ ! -d $1 ] ; then

        echo "No such file or directory"

        exit

        elif [ ! -d $2 ] ; then

         mkdir -p $2

        fi

        srcdir=$(dirname $1)

        srcname=$(basename $1)

        destdir=$2

        destname=$(basename $2)

        destdir="${destdir%/}/"

        # setp1.1:when today is the first day of the month,

        # the programme will move the all the backuped file

        # to another directory.

        if [ $(date +%d) == "01" ] ; then

            if [ $(whereis -b "$destname$(date +%d)") ] ; then

                pushd $(dirname $destdir)

                rm -rf  "$destname$(date +%d)" 1>/dev/null 2>>"${destdir}qvbackup.log"

                popd

            fi

            pushd $(dirname  $destdir)

                mv  "$destname"  "$destname$(date +%d)"

                mkdir -p $2

            popd

        fi

        # step1.2:backup files of SOURCE-DIRECTORY to

        # DEST-DIRECTORY

        backupfile="$(date +%Y-%m-%d-%H-%M-%S)_$srcname.tgz"

        destfile="$destdir$backupfile"

        pushd  $srcdir

        tar -g "${destdir}snapshot" -zcf $destfile  $srcname 1>/dev/null 2>>"${destdir}qvbackup.log"

        retCode=$?

        popd 

    ;;

    "0")

        echo "No parameters, please make sure."

        exit

    ;;

       *)

        echo "Too more parameters, please make sure."

        exit

  ;;

 esac

# setp2:output backup log ,backup information and recover scripts

 rstMsg=""

 pushd $destdir

 if [ "$retCode" == "0" ] ; then

    rstMsg="$(date +%Y-%m-%d-%H-%M-%S) backup OK"

    echo "tar zxf $destfile">>qvrecover.sh

 else

    rstMsg="$(date +%Y-%m-%d-%H-%M-%S) backup ERROR"

 fi

    echo $rstMsg>>qvbackup.log

 popd

    echo $rstMsg

 exit 0

问题是

1.一直备份，但磁盘占满了怎么办，需要自动化监测磁盘使用率。

2.因为组件比较小，使用的是完全备份，是不是可以保持最近一周的不删掉或者最近的五个、十个？