Shell Script Programming

Explanation

Here is the explanation of the script:

1. Purpose

This script greets the user with a time-appropriate message ("Good Morning", "Good Afternoon", or "Good Evening") based on the current hour of the day.

2. Key Concepts

• Command Substitution ($(...)): Executing a system command and storing its output in a variable.
• Variables: Storing data for later use (hour).
• Conditional Logic (if / elif / else): Making decisions based on specific conditions.
• Numeric Comparison (-lt): Shell operator for "less than".

3. Code Walkthrough

• #!/bin/bash
  The Shebang line. It tells the system to execute this file using the Bash interpreter.

• hour=$(date +%H)
  Runs the date +%H command to get the current hour in 24-hour format (00–23) and assigns it to the hour variable.

• if [ $hour -lt 12 ] ... echo "Good Morning"
  Checks if the hour is less than 12 (12:00 AM – 11:59 AM). If true, it outputs "Good Morning".

• elif [ $hour -lt 17 ] ... echo "Good Afternoon"
  If the first condition is false, it checks if the hour is less than 17 (12:00 PM –