shell腳本常見面試題

一、打印九九乘法表
方法一

#外層循環表示9行
for row in `seq 9`
do
        #裏層循環表示列
        for col in `seq $row`
        do
                echo -e $row x $col =  "$[ row*col ]\t\c"
        done
        echo 
done

方法二：

for((i=1;i<=9;i++));do for((j=1;j<=i;j++));do echo -ne "$j X $i = $((i*j))\t";done;echo;done;

方法三：awk寫法

awk 'BEGIN{for(i=1;i<=9;i++){for(j=1;j<=i;j++){printf "%s %-4d","j x i =",i*j}printf "\n"}}'

二、國際象棋棋盤

#輸入1爲兩個空格
read -p "輸入每一個方格的大小(2space=1)：" weight
#八行國際象棋
for i in `seq 8`;do
        for j in `seq $weight`;do
                #奇數行爲紅 綠 紅 綠  .... 
                if [ "$[i%2]" = 1 ];then
                        colour1=41  #紅色
                        colour2=42  #綠色
                else #偶數行爲 綠紅 綠紅 ....
                        colour1=42
                        colour2=41
                fi
                for k in `seq 4`;do #每行8個方塊
                        for n in `seq $weight`;do  #打印2個方塊
                                echo -ne "\033[${colour1}m  \033[0m"
                        done
                        for m in `seq $weight`;do  #打印2個方塊
                                echo -ne "\033[${colour2}m  \033[0m"
                        done
                done
                echo

三、打印等腰三角形

read -p "請輸入三角形的行數:" line
for i in `seq $line`
do
        space=`echo $[line-i]`
        for j in `seq $space`
        do
                echo -n ' '
        done
        for k in `seq $[$i*2-1]`
        do
                echo -n '*'
        done
        echo
done

四、打印下圖

num=9
for i in `seq 1 $num`;do
        let j=2*$i-1
        let m=10-$i
        for l in `seq 1 $m` ;do
                echo -e " \c"
        done

        for k in `seq 1 $j`;do

                let n=$i%2
                if [ $n -eq 0 ];then
                  echo -ne "\e[1;5;3$[i]m$i\e[0m"
                elif [[ $k -eq 1||$k -eq $j ]];then
                  echo -ne "\e[1;5;3$[i]m$i\e[0m"
                else
                  echo -ne "\e[1;3$[i]m$i\e[0m"
                fi
        done
        echo
done
unset i
unset j
unset k
unset l
let j=$num/2-1
for i in `seq 1 $j`;do
        echo -e "\e[1;3$[i]m        666\\e[0m"
done
echo -e "\e[1;34m       66666\\e[0m"

五、打印下圖

#輸入三角形邊長（n個*）
read -p "Please input the triangle side " n
#遍歷n行三角形
for i in `seq $n`
do
                #打印空格
        for j in `seq $[n-i]`
        do
                echo -e " \c"
        done
                #除第一行外打印一個星號
        if [[ "$i" -ne 1 ]]; then
        echo -e "*\c"
        fi
                #除第一行和最後一行打印空格
        if [[ "$i" -ne 1 && "$i" -ne "$n" ]]; then
        {
                for k in `seq $[2*(i-1) -1]`
                do
                echo -e " \c"
                done
        }
        fi
                #最後一行打印星號
        if [[ "$i" -eq "$n"  ]]; then
        {
                k=0
                for k in `seq $[2*i-3]`
                do
                        echo -e "*\c"
                done
        }
        fi
        echo -e "*"
done

六、每隔30秒監控httpd服務是否啓動，若是沒啓動就啓動httpd服務

sleeptime=30
while true
do
        if killall -0 httpd &> /dev/null;then
                true
        else
                systemctl restart httpd
                time=`date +"%F %T" `
                echo "httpd service at "$time" is restarted" >> /app/http.log
        fi
        sleep "$sleeptime"
done

讓腳本在後臺執行不影響前臺正常工做
nohup ./root/scripts/monhttpd.sh &

七、將鏈接服務器次數不少次的客戶端IP加入防火牆

while true
do
        ss -nt | grep ESTAB | tr -s " " ":" | cut -d: -f6 | sort | uniq -c | while read num ip 
        do
                if [ "$num" -gt 2 ];then
                iptables -A INPUT -s "$ip" -j REJECT
                fi
        done
        sleep 3
done

八、後續六個字符串：efbaf275cd、4be9c40b8b、 44b2395c4六、f8c8873ce0、b902c16c8b、ad865d2f63是經過對隨機數變量RANDOM隨機執行命令：
echo $RANDOM|md5sum|cut –c1-10

i=1
while [ "$i" -le 32767 ];do
        ranmd5=`echo $i | md5sum | cut -c1-10`
        case ${ranmd5}  in
                efbaf275cd)
                        echo $i md5 is efbaf275cd
                        ;;
                4be9c40b8b)
                        echo $i md5 is 4be9c40b8b 
                        ;;
                44b2395c46)
                        echo $i md5 is 4be9c40b8b
                        ;;
                f8c8873ce0)
                        echo $i md5 is 4be9c40b8b
                        ;;
                b902c16c8b)
                        echo $i md5 is 4be9c40b8b
                        ;;
                ad865d2f63)
                        echo $i md5 is 4be9c40b8b
                        ;;
        esac
        let i++;
done

九、編寫腳本，利用變量RANDOM生成10個隨機數字，輸出這個10數字，並顯示其中的最大值和最小值（隨機數最大值32767）

i=1
while [ "$i" -le 10 ];do
        random=`echo $RANDOM`
        echo $random
        if [ "$i" = 1 ];then
                max=$random
                min=$random
        else

                if [ "$random" -gt "$max"  ];then
                        max="$random"
                elif [ "$random" -lt "$min" ];then
                        min="$random"
                fi
        fi
        let i+=1
done
echo "max is $max"
echo "min is $min"

十、while循環建立菜單

cat <<EOF
1 gbjd
2 yxrs
3 zizhu
4 liyu
5 quit
EOF
while read -p "please input menu number: " menu;do
        case $menu in
        1|2)
                echo "The price is 15"
                ;;
        3)
                echo "The price is 50"
                ;;
        4)
                echo "The is is 30"
                ;;
        5)
                break
                ;;
        *)
                echo "please input again "
                ;;
        esac
done

select 循環主要用於建立菜單，按數字順序排列的菜單項將顯示在標準錯誤上，並顯示 PS3 提示符，等待用戶輸入

PS3="please input a menu number: "
        select num in huimian mers jdt jikuai quit;do
                reply=`echo $REPLY`
                echo "---------  $reply"
                case "$reply" in
                1|2|huimian|mers)
                         echo "The price is 15"
                         ;;
                3|jdt)
                        echo "The price is 50"
                        ;;
                4|jikuai)
                        echo "The is is 30"
                        ;;
                5)
                        break
                        ;;
                *)
                                                echo "your input is $reply"
                        echo "please input again "
                        ;;
                esac

        done

十一、求100之內全部奇數之和

for ((sum=0,i=1;i<100;i+=2));do let sum+=i;done;echo $sum

十二、求100之內全部能被3整除的數之和

sum=0;i=0;while [ $i -lt 100 ];do let sum+=i;let i+=3;done; echo $sum

1三、隨機生成10之內的數字，實現猜字遊戲，提示比較大或小，相等則退出
方法一

random=`echo $[RANDOM%10]`
read -p "please guess a num: " num
while [ $num -ne $random ];do
        if [ $num -gt $random ];then
                echo "your num is too big"
                read -p "please guess a num again: " num
        elif [ $num -lt $random ];then
                echo "your num is too small"
                read -p "please guess a num again : " num
        fi
done
echo -e "\033[31mcongratulation! \033[31m"

方法二