Shell Programming and Scripting

#!/bin/awk -f

 BEGIN{ 
 for(i=0;i<=10;i++) 
 { 
  if (i <=1 )
  {
   x=0;
   y=1;
   print i;
  }
  else
  {
   z=x+y;
   print z; 
   x=y;
   y=z;
  }
 } 
    }

x=y;
y=z;

#!/bin/awk -f
 BEGIN{                   #### Starting BEGIN section of awk here.
 for(i=0;i<=10;i++)       #### starting a for loop here, in which i is a variable, it's very first value is set to 0 and then it is set to run for less than or equal to value 10, 3rd section of for loop is for incrementing the variable.
 { 
  if (i <=1 )             #### Now here is a if condition where we are checking the value of variable i, either it's value is less than or equal to 1 or not. If YES(TRUE) then execute following statements in block.
  {                       #### Block starts from here when condition above is TRUE, means when value of variable i is either less than or equal to 1.
   x=0;                   #### Setting value of variable named x to 0.
   y=1;                   #### Setting value of variable named y to 1.
   print i;               #### printing the value of variable i here.
  }                       #### Ending the BLOCK here for TRUE condition statements.
  else                    #### mentioning else here, off course if above(if condition) is NOT TRUE(FALSE) then following statements should be executed.
  {                       #### Starting block for statements which will be executed when above if condition will be FALSE.
   z=x+y;                 #### Adding the values of variable named x and y and saving their sum to a variable named z.
   print z;               #### printing the value of variable named z.
   x=y;                   #### Assigning the value of variable y to variable x. As we know = is called assignment operator to assign the values to variables.
   y=z;                   #### Assigning the value of variable named z(which we got from previous step itself) to variable y. Because as per BASIC funda of Fabonacii series is to get the SUM of previous value and current value. eg--> (0(will come from fist condition),1(will come from first condition),1(sum of 0+1),2(sum of 1+1),3(sum of 2+1),5(sum of 3+2) and so on.
  }                       #### Ending the BLOCK here for FALSE conditoin statements.
 }                        #### Closing the BLOCK for, for loop here.
    }                     #### Closing the BEGIN section here.