Shell Script Programming

Explanation

Here is a concise guide to help you understand this Bash script:

1. Purpose

This program takes a text string entered by the user and prints it in reverse order. It achieves this by reading the input string backwards, character by character, and building a new string.

2. Key Concepts

• User Input: Reading input using read -p.
• String Length: Getting total characters in a string using ${#variable}.
• C-Style for Loop: Counting down from a starting number using for (( ... )).
• String Slicing: Extracting individual characters using ${variable:offset:length} syntax.
• String Concatenation: Appending characters onto an existing string variable.

3. Code Walkthrough

• read -p "Enter a string to reverse: " user_string
  Prompts the user to type text and saves it into the variable user_string.

• reversed=""
  Initializes an empty string variable where the reversed text will be stored.

• length=${#user_string}
  Calculates the total number of characters in user_string.

• for (( i=$length-1; i>=0; i-- )); do
  Starts a loop at the last character's index (length - 1) and counts down to 0 (the first character).

• reversed="$reversed${user_string:$i:1}"
  Extracts 1 character from `