Bash Script to Print Fibonacci Series

Use a Bash script with a loop and variables to print the Fibonacci series, for example: n=10; a=0; b=1; for ((i=0; i.

Examples

Inputn=1

Output0

Inputn=5

Output0 1 1 2 3

Inputn=0

Output

How to Think About It

To print the Fibonacci series, start with two numbers 0 and 1. Then repeatedly add the last two numbers to get the next one. Print each number until you reach the desired count.

Algorithm

1

Get the number of terms to print (n).

2

Initialize two variables with 0 and 1 for the first two Fibonacci numbers.

3

Repeat n times: print the current number, calculate the next by adding the last two, then update the variables.

4

Stop after printing n numbers.

Code

bash

n=10
a=0
b=1
for ((i=0; i<n; i++))
do
  echo -n "$a "
  fn=$((a + b))
  a=$b
  b=$fn
done

Output

0 1 1 2 3 5 8 13 21 34 

Dry Run

Let's trace n=5 through the code

1

Start

n=5, a=0, b=1

2

Iteration 1

Print 0, fn=0+1=1, a=1, b=1

3

Iteration 2

Print 1, fn=1+1=2, a=1, b=2

Iteration	a	b	Printed
0	0	1	0
1	1	1	1
2	1	2	1
3	2	3	2
4	3	5	3

Why This Works

Step 1: Initialize variables

Start with a=0 and b=1 as the first two Fibonacci numbers.

Step 2: Print current number

Print the value of a which holds the current Fibonacci number.

Step 3: Calculate next number

Add a and b to get the next Fibonacci number and update a and b accordingly.

Alternative Approaches

Recursive function

bash

fib() {
  if (( $1 <= 1 )); then
    echo $1
  else
    echo $(( $(fib $(( $1 - 1 ))) + $(fib $(( $1 - 2 ))) ))
  fi
}
for ((i=0; i<10; i++)); do fib $i; done

Uses recursion but is slower and less efficient for large n.

Using an array

bash

fib=(0 1)
for ((i=2; i<10; i++)); do
  fib[i]=$(( fib[i-1] + fib[i-2] ))
done
for i in "${fib[@]}"; do echo -n "$i "; done

Stores all Fibonacci numbers in an array for later use but uses more memory.

Complexity: O(n) time, O(1) space

Time Complexity

The loop runs n times, each step does constant work, so time is O(n).

Space Complexity

Only a few variables are used, so space is O(1).

Which Approach is Fastest?

The iterative loop is fastest and most memory efficient compared to recursion or array storage.

Approach	Time	Space	Best For
Iterative loop	O(n)	O(1)	Simple and efficient for all n
Recursive function	O(2^n)	O(n)	Educational but slow for large n
Array storage	O(n)	O(n)	When you need all Fibonacci numbers stored