for循环的乘法口诀；图形表示—矩形；正直角三角；倒直角三角；反直角；正等腰三角；倒等腰三角；菱形；梯形；平行四边形

一、乘法口诀

#/bin/bash
#9*9
for ((i=1; i<=9; i++))
do
 for ((b=1; b<=$i; b++))
  do
  let c=$i*$b
  echo -n -e "$i*$b=$c\t"
  done
echo ""
done

第二种while写
#/bin/bash
#9*9
i=1
while [ $i -le 9 ]
do
 b=1
 while [ $b -le $i ]
 do
 let c=$i*$b
 echo -n -e "$i*$b=$c\t"
 let b++
 done
let i++
echo ""
done

二、for表示一条直线

#/bin/bash
for ((i=1; i<=20; i++))
do
  echo -n "*"    ///-n 不换行输出
done
  echo ""

三、矩形（长方形）

#/bin/bash
for ((i=1; i<=20; i++))
do
 for ((a=1; a<=10; a++))
 do
 echo -n "*"
done
echo "*"
done

四、正直角三角形

#/bin/bash
for ((i=1; i<=10; i++))
 do
  for ((a=1; a<=$i; a++))
   do
     echo -n "*"  ///不换行输出
   done
 echo ""    /// 输出空行
 done

五、倒直角三角形

#/bin/bash
for ((a=1; a<=10; a++))
do
 for ((b=1; b<=$a; b++))
  do
    echo -n " "
  done
 for ((c=10; c>=$a; c--))
  do
    echo -n "*"
  done
echo ""
done

六、反直角三角形

#/bin/bash
for ((a=1; a<=10; a++))
do
 for ((b=10; b>=$a; b--))
   do
    echo -n " "
   done
 for ((c=1; c<=$a; c++))
  do
   echo -n "*"
  done
echo ""
done

七、倒反直角三角形

#/bin/bash
for ((a=1; a<=10; a++))
do
 for ((b=10; b>=$a; b--))
  do
   echo -n "*"
  done
 for ((c=1; c<=10; c++))
  do
   echo -n " "
  done
echo ""
done

八、正等腰三角形

#/bin/bash
#正等腰三角
for ((i=1; i<=10; i++))
do
   for ((a=10; a>=$i; a--))
      do
        echo -n " "
      done
   for ((b=1; b<=$i; b++))
      do
         echo -n "*"
      done
   for ((c=2; c<=$i; c++))
      do
         echo -n "*"
      done
echo ""
done

九、倒等腰三角形

#/bin/bash
for ((i=1; i<=10; i++))
do
 for ((a=1; a<=$i; a++))
 do
   echo -n " "
 done
 for ((b=10; b>=$i; b--))
 do
   echo -n "*"
 done
 for ((c=9; c>=$i; c--))
 do
   echo -n "*"
 done
echo ""
done

十、菱形

#/bin/bash
for ((i=1; i<=10; i++))
do
   for ((a=10; a>=$i; a--))
      do
        echo -n " "
      done
   for ((b=1; b<=$i; b++))
      do
         echo -n "*"
      done
   for ((c=2; c<=$i; c++))
      do
         echo -n "*"
      done
echo ""
done
for ((i=1; i<=9; i++))
do
   for ((d=0; d<=$i; d++))
     do
       echo -n " "
     done
   for ((e=9; e>=$i; e--))
     do
       echo -n "*"
     done
   for ((f=8; f>=$i; f--))
     do
       echo -n "*"
     done
echo ""
done

十一、等腰梯形

在两个直角三角形中插入矩形的表达式

#/bin/bash
for ((a=1; a<=10; a++))
 do
  for ((b=10; b>=$a; b--))
   do
     echo -n " "
   done
  for ((c=1; c<=$a; c++))
   do
     echo -n "*"
   done
  for ((e=1; e<=6; e++))         ///插入矩形的for表达式
   do
    echo -n "*"
   done
  for ((f=1; f<=5; f++))
   do
    echo -n "*"
   done                        ///长为6个*宽为5个*的矩形表达式
  for ((d=1; d<=$a; d++))
   do
     echo -n "*"
   done
echo ""
done

十二、平行四边形

#/bin/bash
for ((a=1; a<=10; a++))    /// 空格的直角三角形
do
  for ((b=1; b<=$a; b++))
    do
     echo -n " "
    done
  for ((c=1; c<=6; c++))     //插入矩形
    do
      echo -n "*"
    done
 echo ""
done