C-style for loop in Bash Scripting

Introduction

A C-style for loop helps you repeat a set of commands a specific number of times, just like counting steps in a recipe.

When you want to run a command exactly 5 times.

When you need to process files numbered from 1 to 10.

When you want to count down from 10 to 1.

When you want to repeat a task with a specific start, end, and step.

When you want to automate repetitive tasks in a script.

Syntax

Bash Scripting

for (( initialization; condition; increment )); do
  commands
 done

Initialization sets the starting point, like setting a counter to 0.

Condition is checked before each loop; if false, the loop stops.

Examples

Counts from 0 to 4 and prints each number.

Bash Scripting

for (( i=0; i<5; i++ )); do
  echo $i
done

Counts down from 10 to 1 and prints each number.

Bash Scripting

for (( i=10; i>0; i-- )); do
  echo $i
done

Counts from 1 to 10 in steps of 2, printing odd numbers.

Bash Scripting

for (( i=1; i<=10; i+=2 )); do
  echo $i
done

Sample Program

This script prints 'Step' followed by numbers 1 to 5, showing a simple count.

Bash Scripting

#!/bin/bash
for (( i=1; i<=5; i++ )); do
  echo "Step $i"
done

Important Notes

Make sure to use double parentheses (( )) for C-style loops in bash.

Remember to include spaces around the semicolons inside the loop syntax.

Use 'do' and 'done' to mark the start and end of the loop commands.

Summary

C-style for loops repeat commands with a clear start, stop, and step.

They are useful for counting and repeating tasks in bash scripts.

Syntax uses double parentheses and semicolons to separate parts.