Bash Script to Print Alphabet Pattern with Loop

Use a Bash script with a loop and printf to print letters from A to Z in a pattern, for example: for i in {A..Z}; do printf "%s " "$i"; done; echo.

Examples

InputPrint letters A to E

OutputA B C D E

InputPrint letters A to Z

OutputA B C D E F G H I J K L M N O P Q R S T U V W X Y Z

InputPrint letters A to C

OutputA B C

How to Think About It

To print an alphabet pattern in Bash, think of the alphabet as a sequence of letters from A to Z. Use a loop to go through each letter and print it. You can control how many letters to print by setting the loop range. Use printf to print letters on the same line with spaces.

Algorithm

1

Decide the range of letters to print (e.g., A to E).

2

Start a loop from the first letter to the last letter.

3

In each loop iteration, print the current letter followed by a space.

4

After the loop ends, print a newline to finish the pattern.

Code

bash

for letter in {A..E}; do
  printf "%s " "$letter"
done
printf "\n"

Output

A B C D E 

Dry Run

Let's trace printing letters A to E through the code

1

Start loop

letter = A

2

Print letter

Output: 'A '

3

Next letter

letter = B, Output: 'A B '

Iteration	Letter	Output So Far
1	A	A
2	B	A B
3	C	A B C
4	D	A B C D
5	E	A B C D E

Why This Works

Step 1: Loop over letters

The for loop iterates over letters from A to E using brace expansion.

Step 2: Print each letter

Inside the loop, printf "%s " prints the current letter followed by a space without a newline.

Step 3: Print newline

After the loop, printf "\n" prints a newline to move to the next line.

Alternative Approaches

Using ASCII codes with printf

bash

for ((i=65; i<=69; i++)); do
  printf "%c " "$i"
done
printf "\n"

Uses ASCII decimal codes for letters; more flexible for custom ranges but less readable.

Using seq and awk

bash

seq 65 69 | awk '{printf "%c ", $1} END {print ""}'

Uses external tools to print letters; useful if you want to combine with other commands.

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

Time Complexity

The loop runs once per letter, so time grows linearly with the number of letters printed.

Space Complexity

The script uses constant extra space, only storing the current letter in the loop.

Which Approach is Fastest?

Using brace expansion is fastest and simplest in Bash; ASCII code loops add complexity but allow more control.

Approach	Time	Space	Best For
Brace Expansion	O(n)	O(1)	Simple alphabet loops
ASCII Codes with printf	O(n)	O(1)	Custom letter ranges
seq and awk	O(n)	O(1)	Combining with other commands