How to Create and Use LSP Files in AutoCAD

AutoCAD is a powerful design software that allows users to automate repetitive tasks through LISP (List Processing) programming. LSP files, which contain AutoLISP code, enable users to customize AutoCAD functionalities and improve productivity. This guide will walk you through creating and using LSP files in AutoCAD.

Creating a LSP File

1. Open a Text Editor:
   • Use a simple text editor such as Notepad or a code editor like Notepad++.
   • Avoid using word processors like Microsoft Word, as they may add formatting that can corrupt the file.
2. Write the AutoLISP Code:
   • AutoLISP uses a syntax similar to Lisp programming. Below is an example of a simple LISP routine that draws a circle at a user-specified point with a default radius:

     (defun c:mycircle ()
       (setq pt (getpoint "Select center point: "))
       (setq rad 5) ; Default radius
       (command "CIRCLE" pt rad)
       (princ)
     )

3. Save the File:
   • Save the file with an .lsp extension (e.g., mycommands.lsp).
   • Ensure the encoding is set to plain text.

Loading and Running an LSP File in AutoCAD

Loading the LSP File

There are multiple ways to load an LSP file into AutoCAD:

1. Using the APPLOAD Command:
   • Type APPLOAD in the command line and press Enter.
   • Click on “Load” and browse to the location of your .lsp file.
   • Select the file and click “Open” to load it.
2. Loading Automatically at Startup:
   • Place the .lsp file in AutoCAD’s startup suite by clicking the “Contents” button in the APPLOAD dialog box and adding the file.
   • This ensures that the LSP file loads every time AutoCAD starts.
3. Loading via the Command Line:
   • Type (load "C:/path/to/yourfile.lsp") in the command line and press Enter.
   • Replace C:/path/to/yourfile.lsp with the actual file path.

Running an AutoLISP Command

Once the LSP file is loaded, execute the custom command by typing its defined name at the command prompt. For the example above, type mycircle and press Enter to run the function.

Editing and Enhancing LSP Files

To modify an existing LSP file:

1. Open the file in a text editor.
2. Make changes to the AutoLISP code.
3. Save the file and reload it in AutoCAD using one of the methods above.

For more advanced functionality, you can:

• Use conditional statements (if, cond)
• Implement loops (while, repeat)
• Store and retrieve user preferences
• Interact with AutoCAD entities through the entget and entmod functions

LSP files provide an excellent way to automate repetitive tasks and enhance productivity in AutoCAD. By creating custom AutoLISP routines, loading them properly, and executing commands, users can streamline their workflow and reduce manual input. Whether you’re a beginner or an advanced user, learning AutoLISP can significantly improve your efficiency in AutoCAD.