Print Numbers from 1 to N in Bash Scripting

In this tutorial, you will learn how to print numbers from 1 to N in a Bash script using loops, specifically the for loop in Bash.

Using a For Loop to Print Numbers from 1 to N

The most common way to print numbers from 1 to N is by using a for loop.

Here’s an example that prints numbers from 1 to N:

print_numbers.sh

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#!/bin/bash
# Prompt the user for the value of N
echo "Enter the number N:"
read N

# Print numbers from 1 to N using a for loop
for ((i=1; i<=N; i++))
do
  echo $i
done

Output

Enter the number N:
5
1
2
3
4
5

Explanation:

  1. Prompt the user for input: The script uses the echo command to display the message "Enter the number N:", prompting the user to input a value for N.
  2. Read the user input: The read command captures the user’s input and stores it in the variable N.
  3. Use a for loop with C-style syntax: The for loop is defined using C-style syntax:
    • Initialization: i=1, starting the loop from 1.
    • Condition: i<=N, ensuring the loop continues as long as i is less than or equal to N.
    • Increment: i++, incrementing the value of i by 1 in each iteration.
  4. Print each number: During each iteration of the loop, the current value of i is printed to the console using the echo command.
  5. End of script: Once the loop completes (after printing all numbers from 1 to N), the script ends successfully.

Using a For Loop with a Range to Print Numbers from 1 to N

Alternatively, you can use a range in the for loop to print numbers from 1 to N. This method uses the {} syntax in the loop declaration:

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for i in {1..N}

Here’s an example of how to print numbers from 1 to N using this method:

print_numbers.sh

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#!/bin/bash
# Prompt the user for the value of N
echo "Enter the number N:"
read N

# Print numbers from 1 to N using a range in the for loop
for i in $(seq 1 $N)
do
  echo $i
done

Output

Enter the number N:
5
1
2
3
4
5

Explanation:

  1. Prompt the user for input: The script displays the message "Enter the number N:" to prompt the user to input a value for N.
  2. Read the user input: The read command takes the user’s input and assigns it to the variable N.
  3. Use a for loop to iterate from 1 to N: The seq command generates a sequence of numbers from 1 to N. The for loop iterates over this sequence, assigning each value to the variable i.
  4. Print each number: During each iteration, the script uses the echo command to print the current value of i to the console.
  5. End of script: Once the loop completes (after printing all numbers from 1 to N), the script ends successfully.