Shell Bash

[Zeno's cat]

 #!/bin/bash
  2 if [ $# = 3 ]
  3 then
  4     echo "input num=3"
  5     op=$2
  6     op_a=$1
  7     op_b=$3
  8 
  9         if [ $op = "add" ]
 10         then
 11             c= expr $op_a + $op_b
 12             echo  "$op_a + $op_b = $c"
 13 
 14         elif [ $op = "sub" ]
 15         then
 16             c= expr $op_a - $op_b
 17             echo  "$op_a - $op_b = $c"  
 18 
 19         elif [ $op = "mul" ]
 20         then
 21             c= expr $op_a \* $op_b
 22             echo  "$op_a * $op_b = $c"  
 23 
 24         elif [ $op = "div" ]
 25         then
 26             c= expr $op_a / $op_b
 27             echo  "$op_a / $op_b = $c"
 28 
 29         else
 30             echo "Unknow op"
 31         fi
 32 
 33 else
 34     echo "input num error"
 35 fi

编辑运行完毕以后，是如图中2L所示，可是不应是在同一列吗？是我bash设置有问题还是什么原因？

[Zeno's cat]

[Zeno's cat]

小白刚学shell bash，代码如上，求轻拍，求指点。