Lesson 5.06 - Working with User Input

🎯 Lesson 5-06 – Working with User Input

Learn how to collect numbers, strings, points, and object selections using AutoLISP’s built-in input functions.

📚 What You’ll Learn

By the end of this lesson, you’ll be able to:

Prompt the user for integers, real numbers, strings, and coordinates
Use initget to control input behavior
Select objects interactively with entsel
Validate and handle input effectively in custom commands

🧠 Why It Matters

User input is the gateway to interactive automation in AutoCAD. By mastering these functions, you can build routines that adapt to user decisions, geometry selections, and numeric data—all essential for custom workflows.

🛠️ Tools You’ll Use

Function	Purpose
`getint`	Get an integer from the user
`getreal`	Get a real (decimal) number
`getstring`	Get text input from the user
`getpoint`	Let the user click or enter a coordinate
`initget`	Add input constraints (e.g., keywords, no NULL)
`entsel`	Prompt user to select an object

🧭 Lesson Structure

1️⃣ Getting Numbers and Text

Use these functions to collect basic input from the user:

(setq age (getint "\nEnter your age: "))
(setq price (getreal "\nEnter price: "))
(setq name (getstring "\nEnter your name: "))

Function	Expected Input	Example Input	Returns

getint Whole number 45 45

getreal Decimal number 129.99 129.99

getstring Text string John "John"

🔹 Tip: Use (getstring T ...) to allow spaces in string input.

2️⃣ Getting Points from User

You can collect coordinate input using getpoint:

(setq pt (getpoint "\nPick a point: "))

Input Type	Example Result
Mouse click	`(100.0 200.0 0.0)`
Typed value	`50,100` becomes `(50.0 100.0 0.0)`

Use points in drawing commands like LINE, CIRCLE, or for geometry logic.

3️⃣ Controlling Input with `initget`

Use initget to filter or extend input:

(initget 1 "Yes No")
(setq response (getkword "\nDo you want to continue? [Yes/No]: "))

ode	Description

(initget 1) Disallows null input (user must respond)

(initget "Yes No") Accepts only the listed keywords

(getkword ...) Collects a keyword from the user

🚨 Always call initget before the input function!

4️⃣ Selecting Objects with `entsel`

Use entsel to let the user click an entity in the drawing:

(setq sel (entsel "\nSelect an object: "))

User hit escape or didn’t click

You can pass the result to entget to retrieve object data.

✅ Lesson Checklist

Task	Completed
Used `getint`, `getreal`, `getstring`, and `getpoint`	☐
Restricted input using `initget` and `getkword`	☐
Let user pick an object using `entsel`	☐
Applied input in a custom routine	☐

📌 Quick Tips

Tip	Why It Helps
Use `initget 1` to make input required	Prevents unintentional `nil` values
Always test `entsel` result for `nil`	Avoids crashes if the user cancels
Add `\n` before prompt strings	Ensures clean, new-line display in command line
Use `getstring T` to allow spaces in names	Helps for full names or titles

🧩 Real-World Applications

Scenario	Input Function Used	Purpose
Dimension labeling	`getstring`, `getreal`	Add dynamic text or dimensions
Interactive scripts	`getpoint`, `getint`, `initget`	Prompt-driven workflows
Object analysis	`entsel`	Select and inspect drawing entities

📁 Files and Resources

File / Resource	Description
`user_input_demo.lsp`	Routine demonstrating all input types
`input_practice.txt`	Practice exercises for capturing different inputs
`initget_cheatsheet.docx`	Reference guide for using `initget` effectively

📖 Review Table

Function	Use Case	Example
`getint`	Whole number input	`(getint "\\nEnter value: ")`
`getreal`	Decimal number input	`(getreal "\\nEnter height: ")`
`getstring`	Text input	`(getstring "\\nEnter name: ")`
`getpoint`	Pick or type coordinates	`(getpoint "\\nPick location: ")`
`initget`	Control allowed input or make required	`(initget 1 "Yes No")`
`entsel`	Select object	`(entsel "\\nSelect entity: ")`