Script Planning & Design

Before you write a single line of code, you need a plan. A well-designed script is easier to build, debug, and maintain.

Why Plan Your Script?

A plan helps you:

• Understand what the script needs to do before coding
• Identify all the steps in the right order
• Know what input and output you need
• Catch problems early (much easier than debugging later)
• Create a flowchart that guides development

The Design Process

1. Define the Goal

Write a clear, single sentence describing what your script does.

Example: “Monitor free memory every 60 seconds and log results to a SQL file”

2. List Input Data

What information does the script need from the user or system?

• User arguments (command-line parameters)
• File paths or configuration
• System information
• User choices (menu options)

Example inputs:

• Duration in seconds (from user argument)
• Output filename (from user argument)
• Machine hostname (from system)

3. List Output Data

What does the script produce or display?

• Files created or modified
• Console messages
• Choices presented to the user

Example outputs:

• Warning message if file exists
• Menu options (1/2/9)
• Results file location
• Progress display (free memory readings)

4. Break Down the Steps

List every step your script performs, in order. Be specific.

Example steps:

1. Set default values for variables
2. Check if user provided different values
3. Check if output file already exists
4. If exists, ask user what to do (add/delete/quit)
5. Calculate stop time
6. Loop: check memory, write to file, show progress
7. Display results location
8. Ask user if they want to open the file

5. Create a Flowchart

A flowchart shows the flow of your script visually:

• Ovals (Pills) = Start/End
• Rectangles = Actions or processes
• Diamonds = Decisions (if/else)
• Arrows = Flow direction

Use your steps above to draw the flowchart. Include every decision point (diamonds) where your script asks a question or makes a choice.

Rules of Thumb:

• Start at the top
• End at the bottom
• Every diamond (decision) has two paths: Yes and No
• Every action leads to the next step
• Loops circle back to earlier steps

6. Validate Your Plan

Before coding, ask:

• Does every input have a purpose?
• Does every step have a clear outcome?
• Are all decisions handled (Yes/No paths)?
• Is the order logical?
• Have I covered edge cases (file exists, invalid input, etc.)?

Example: Memory Monitor Script

Goal: Monitor free memory for a specified duration and save results to a SQL file.

Input data:

• Duration in seconds (default: 60, user can override)
• Output filename (default: MemoryResults.sql, user can override)
• Machine hostname (automatic from system)
• User choice if file exists (menu: add/delete/quit)

Output data:

• Warning message if output file already exists
• Menu options: [1] Add results, [2] Delete and start fresh, [9] Quit
• Console display of current free memory
• Results file location
• Offer to open the file when done

Steps:

1. Set default variable values (60 seconds, MemoryResults.sql, hostname)
2. Check if user provided arguments; override defaults if valid
3. Check if output file exists
   • If yes: ask user (add/delete/quit)
   • If no: create file
4. Calculate when to stop (current time + duration)
5. Display what will happen (clear screen, show parameters)
6. Loop until stop time reached:
   • Get current free memory
   • Write to file with timestamp
   • Show progress indicator
7. Clear screen and show file location
8. Ask if user wants to open file
9. Display completion message

This plan becomes your flowchart and guides every line of code you write.