【shell】Linux shell 之 打印99乘法表詳解
阿新 • • 發佈：2018-03-26
shell linux 腳本
打印99乘法表在任何語言中都是一個必寫的程序，特別是學習了循環之後。
打印99乘法表第一步
眾所周知，99乘法表的格式為x * y = z
所以我們至少需要兩個參數，一個為x，一個為y，這裏我們使用 i 和 j 來表示。
x 和 y 都不會超過 9 ，並具有一定的規律，比如 1 x 2,1 x 3
根據上面的分析，我們首先需要把 i 和 j 先寫出來，寫就需要用到我們的雙層for循環了。
#!/bin/bash -
for i in `seq 9`
do
for j in `seq 9`
do
echo $j,$i
done
done
執行結果
[root@XiaoPeng scripts]# bash chengfa.sh 1,1 2,1 3,1 4,1 5,1 6,1 7,1 8,1 9,1 1,2 2,2 3,2 4,2 5,2 6,2 7,2 8,2 9,2 1,3 2,3 3,3 4,3 5,3 6,3 7,3 8,3 9,3 1,4 2,4 3,4 4,4 5,4 6,4 7,4 8,4 9,4 1,5 2,5 3,5 4,5 5,5 6,5 7,5 8,5 9,5 1,6 2,6 3,6 4,6 5,6 6,6 7,6 8,6 9,6 1,7 2,7 3,7 4,7 5,7 6,7 7,7 8,7 9,7 1,8 2,8 3,8 4,8 5,8 6,8 7,8 8,8 9,8 1,9 2,9 3,9 4,9 5,9 6,9 7,9 8,9 9,9 [root@XiaoPeng scripts]#
到了這裏，大家可能已經找到一點規律了，i 和 j我們已經得出來了，所以我們要給 i 和 j 進行一個乘法運算即可。
!/bin/bash -
for i in `seq 9`
do
for j in `seq 9`
do
echo "$i x $j = `echo $(($i*$j))`" # 運算
done
done執行結果
[root@XiaoPeng scripts]# bash chengfa.sh 1 x 1 = 1 1 x 2 = 2 1 x 3 = 3 1 x 4 = 4 1 x 5 = 5 1 x 6 = 6 1 x 7 = 7 1 x 8 = 8 1 x 9 = 9 2 x 1 = 2 2 x 2 = 4 2 x 3 = 6 2 x 4 = 8 2 x 5 = 10 2 x 6 = 12 2 x 7 = 14 2 x 8 = 16 2 x 9 = 18 3 x 1 = 3 3 x 2 = 6 3 x 3 = 9 3 x 4 = 12 3 x 5 = 15 3 x 6 = 18 3 x 7 = 21 3 x 8 = 24 3 x 9 = 27 4 x 1 = 4 4 x 2 = 8 4 x 3 = 12 4 x 4 = 16 4 x 5 = 20 4 x 6 = 24 4 x 7 = 28 4 x 8 = 32 4 x 9 = 36 5 x 1 = 5 5 x 2 = 10 5 x 3 = 15 5 x 4 = 20 5 x 5 = 25 5 x 6 = 30 5 x 7 = 35 5 x 8 = 40 5 x 9 = 45 6 x 1 = 6 6 x 2 = 12 6 x 3 = 18 6 x 4 = 24 6 x 5 = 30 6 x 6 = 36 6 x 7 = 42 6 x 8 = 48 6 x 9 = 54 7 x 1 = 7 7 x 2 = 14 7 x 3 = 21 7 x 4 = 28 7 x 5 = 35 7 x 6 = 42 7 x 7 = 49 7 x 8 = 56 7 x 9 = 63 8 x 1 = 8 8 x 2 = 16 8 x 3 = 24 8 x 4 = 32 8 x 5 = 40 8 x 6 = 48 8 x 7 = 56 8 x 8 = 64 8 x 9 = 72 9 x 1 = 9 9 x 2 = 18 9 x 3 = 27 9 x 4 = 36 9 x 5 = 45 9 x 6 = 54 9 x 7 = 63 9 x 8 = 72 9 x 9 = 81
到這一步之後，整個雛形就出現了，這時候我們會發現一個問題，那就是每個公式都是單獨的一行，所以我們需要修改一些程序，echo 中的 -n 參數便是取消跨行輸出。
修改部分
echo -n "$i x $j = `echo $(($i*$j))`"執行結果
[root@XiaoPeng scripts]# bash chengfa.sh
1 x 1 = 11 x 2 = 21 x 3 = 31 x 4 = 41 x 5 = 51 x 6 = 61 x 7 = 71 x 8 = 81 x 9 = 92 x 1 = 22 x 2 = 42 x 3 = 62 x 4 = 82 x 5 = 102 x 6 = 122 x 7 = 142 x 8 = 162 x 9 = 183 x 1 = 33 x 2 = 63 x 3 = 93 x 4 = 123 x 5 = 153 x 6 = 183 x 7 = 213 x 8 = 243 x 9 = 274 x 1 = 44 x 2 = 84 x 3 = 124 x 4 = 164 x 5 = 204 x 6 = 244 x 7 = 284 x 8 = 324 x 9 = 365 x 1 = 55 x 2 = 105 x 3 = 155 x 4 = 205 x 5 = 255 x 6 = 305 x 7 = 355 x 8 = 405 x 9 = 456 x 1 = 66 x 2 = 126 x 3 = 186 x 4 = 246 x 5 = 306 x 6 = 366 x 7 = 426 x 8 = 486 x 9 = 547 x 1 = 77 x 2 = 147 x 3 = 217 x 4 = 287 x 5 = 357 x 6 = 427 x 7 = 497 x 8 = 567 x 9 = 638 x 1 = 88 x 2 = 168 x 3 = 248 x 4 = 328 x 5 = 408 x 6 = 488 x 7 = 568 x 8 = 648 x 9 = 729 x 1 = 99 x 2 = 189 x 3 = 279 x 4 = 369 x 5 = 459 x 6 = 549 x 7 = 639 x 8 = 729 x 9 = 81[root@XiaoPeng scripts]# 到了步之後，大家會發現，所有的變量都是挨著的，怎麽改呢？我們只需要在echo 後面加兩個空格就好啦！
修改部分
echo -n "$i x $j = `echo $(($i*$j))` ” # ”前面加了兩個空格。執行結果
1 x 1 = 1 1 x 2 = 2 1 x 3 = 3 1 x 4 = 4 1 x 5 = 5 1 x 6 = 6 1 x 7 = 7 1 x 8 = 8 1 x 9 = 9 2 x 1 = 2 2 x 2 = 4 2 x 3 = 6 2 x 4 = 8 2 x 5 = 10 2 x 6 = 12 2 x 7 = 14 2 x 8 = 16 2 x 9 = 18 3 x 1 = 3 3 x 2 = 6 3 x 3 = 9 3 x 4 = 12 3 x 5 = 15 3 x 6 = 18 3 x 7 = 21 3 x 8 = 24 3 x 9 = 27 4 x 1 = 4 4 x 2 = 8 4 x 3 = 12 4 x 4 = 16 4 x 5 = 20 4 x 6 = 24 4 x 7 = 28 4 x 8 = 32 4 x 9 = 36 5 x 1 = 5 5 x 2 = 10 5 x 3 = 15 5 x 4 = 20 5 x 5 = 25 5 x 6 = 30 5 x 7 = 35 5 x 8 = 40 5 x 9 = 45 6 x 1 = 6 6 x 2 = 12 6 x 3 = 18 6 x 4 = 24 6 x 5 = 30 6 x 6 = 36 6 x 7 = 42 6 x 8 = 48 6 x 9 = 54 7 x 1 = 7 7 x 2 = 14 7 x 3 = 21 7 x 4 = 28 7 x 5 = 35 7 x 6 = 42 7 x 7 = 49 7 x 8 = 56 7 x 9 = 63 8 x 1 = 8 8 x 2 = 16 8 x 3 = 24 8 x 4 = 32 8 x 5 = 40 8 x 6 = 48 8 x 7 = 56 8 x 8 = 64 8 x 9 = 72 9 x 1 = 9 9 x 2 = 18 9 x 3 = 27 9 x 4 = 36 9 x 5 = 45 9 x 6 = 54 9 x 7 = 63 9 x 8 = 72 9 x 9 = 81 好看多了吧，但是我們還會發現，輸出的結果並不會換行，因為99乘法表是需要換行的，1 x 1 =2 一行，1 x 2 =2 2 x 2 = 4 一行。所以我們需要把程序繼續修改，比如我們規定，每當 j 循環結束我們就換行一次。
修改部分
for i in `seq 9`
do
for j in `seq 9`
do
echo -n "$i x $j = `echo $(($i*$j))` "
done
echo "" # 打印空行
don執行結果
[root@XiaoPeng scripts]# bash chengfa.sh
1 x 1 = 1 1 x 2 = 2 1 x 3 = 3 1 x 4 = 4 1 x 5 = 5 1 x 6 = 6 1 x 7 = 7 1 x 8 = 8 1 x 9 = 9
2 x 1 = 2 2 x 2 = 4 2 x 3 = 6 2 x 4 = 8 2 x 5 = 10 2 x 6 = 12 2 x 7 = 14 2 x 8 = 16 2 x 9 = 18
3 x 1 = 3 3 x 2 = 6 3 x 3 = 9 3 x 4 = 12 3 x 5 = 15 3 x 6 = 18 3 x 7 = 21 3 x 8 = 24 3 x 9 = 27
4 x 1 = 4 4 x 2 = 8 4 x 3 = 12 4 x 4 = 16 4 x 5 = 20 4 x 6 = 24 4 x 7 = 28 4 x 8 = 32 4 x 9 = 36
5 x 1 = 5 5 x 2 = 10 5 x 3 = 15 5 x 4 = 20 5 x 5 = 25 5 x 6 = 30 5 x 7 = 35 5 x 8 = 40 5 x 9 = 45
6 x 1 = 6 6 x 2 = 12 6 x 3 = 18 6 x 4 = 24 6 x 5 = 30 6 x 6 = 36 6 x 7 = 42 6 x 8 = 48 6 x 9 = 54
7 x 1 = 7 7 x 2 = 14 7 x 3 = 21 7 x 4 = 28 7 x 5 = 35 7 x 6 = 42 7 x 7 = 49 7 x 8 = 56 7 x 9 = 63
8 x 1 = 8 8 x 2 = 16 8 x 3 = 24 8 x 4 = 32 8 x 5 = 40 8 x 6 = 48 8 x 7 = 56 8 x 8 = 64 8 x 9 = 72
9 x 1 = 9 9 x 2 = 18 9 x 3 = 27 9 x 4 = 36 9 x 5 = 45 9 x 6 = 54 9 x 7 = 63 9 x 8 = 72 9 x 9 = 81 這時候大家會發現，我們正常的乘法表是直角三角形，現在的是矩形輸出，為什麽呢？大家可能發現了，因為我們有部分的公式是重復的，如果 1 x 2 = 2和 2 x 1 =2 重復了，那麽怎麽去解決呢？大家可以發現一個規律，1 x 2 =2, 2 x 2 = 4 ，還有 1 x 3 = 3 2 x 3 = 6 3 x 3 = 9 ，同一行中，前面一個數不會大於後面的數，即 j x i = z，j 不會大於 i
修改部分
for i in `seq 9`
do
for j in `seq 9`
do
[ $j -le $i ] && echo -n "$i x $j = `echo $(($i*$j))` " # 如果 j 小與等於 i 才會打印式子
done
echo ""
done執行結果
[root@XiaoPeng scripts]# bash chengfa.sh
1 x 1 = 1
2 x 1 = 2 2 x 2 = 4
3 x 1 = 3 3 x 2 = 6 3 x 3 = 9
4 x 1 = 4 4 x 2 = 8 4 x 3 = 12 4 x 4 = 16
5 x 1 = 5 5 x 2 = 10 5 x 3 = 15 5 x 4 = 20 5 x 5 = 25
6 x 1 = 6 6 x 2 = 12 6 x 3 = 18 6 x 4 = 24 6 x 5 = 30 6 x 6 = 36
7 x 1 = 7 7 x 2 = 14 7 x 3 = 21 7 x 4 = 28 7 x 5 = 35 7 x 6 = 42 7 x 7 = 49
8 x 1 = 8 8 x 2 = 16 8 x 3 = 24 8 x 4 = 32 8 x 5 = 40 8 x 6 = 48 8 x 7 = 56 8 x 8 = 64
9 x 1 = 9 9 x 2 = 18 9 x 3 = 27 9 x 4 = 36 9 x 5 = 45 9 x 6 = 54 9 x 7 = 63 9 x 8 = 72 9 x 9 = 81 至此完畢。
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【shell】Linux shell 之 打印99乘法表詳解