Bash Script to Print Star Pattern with Loop

Use a Bash script with a for loop and echo to print stars line by line, for example: for i in {1..5}; do echo "$(printf '*%.0s' $(seq 1 $i))"; done prints a simple star pattern.

Examples

Input5

Output* ** *** **** *****

Input3

Output* ** ***

Input1

Output*

How to Think About It

To print a star pattern, think of printing one line at a time. Each line has a number of stars equal to the line number. Use a loop to count from 1 to the input number, and print stars accordingly.

Algorithm

1

Get the number of lines to print from the user.

2

Start a loop from 1 to the number of lines.

3

For each iteration, print stars equal to the current loop number.

4

Move to the next line after printing stars.

Code

bash

#!/bin/bash
read -p "Enter number of lines: " n
for ((i=1; i<=n; i++))
do
  printf '%*s\n' "$i" '' | tr ' ' '*'
done

Output

*
**
***
****
*****

Dry Run

Let's trace printing 3 lines of stars through the code

1

Input

User enters n=3

2

First loop iteration

i=1, print 1 star: *

3

Second loop iteration

i=2, print 2 stars: **

4

Third loop iteration

i=3, print 3 stars: ***

i	Stars Printed
1	*
2	**
3	***

Why This Works

Step 1: Loop controls lines

The for loop runs from 1 to the input number, controlling how many lines to print.

Step 2: Printing stars

Inside the loop, printf with tr prints the exact number of stars for the current line.

Step 3: New line after each print

Each iteration prints stars followed by a newline, creating the pattern line by line.

Alternative Approaches

Using nested loops

bash

#!/bin/bash
read -p "Enter number of lines: " n
for ((i=1; i<=n; i++))
do
  for ((j=1; j<=i; j++))
  do
    echo -n "*"
  done
  echo
 done

Uses two loops: outer for lines, inner for stars; more explicit but longer code.

Using seq and xargs

bash

#!/bin/bash
read -p "Enter number of lines: " n
for i in $(seq 1 $n)
do
  seq -s '*' $i | tr -d '[:digit:] '
done

Uses external commands seq and tr; less efficient but shows command chaining.

Complexity: O(n^2) time, O(1) space

Time Complexity

The script prints stars in nested loops or repeated commands, resulting in roughly n*(n+1)/2 operations, which is O(n^2).

Space Complexity

The script uses constant extra space, only storing counters and printing directly without extra arrays.

Which Approach is Fastest?

Using printf with tr is faster and cleaner than nested loops or external commands.

Approach	Time	Space	Best For
printf with tr	O(n^2)	O(1)	Simple and efficient star printing
Nested loops	O(n^2)	O(1)	Clear logic, easy to understand
seq and xargs	O(n^2)	O(1)	Demonstrates command chaining, less efficient