How to Use DIESEL Expressions in AutoCAD: Syntax and Examples
In AutoCAD,
DIESEL expressions are used to create dynamic text by embedding simple scripts inside fields or text objects. You write a DIESEL expression using the syntax %% , where the expression can include functions, variables, and operators to calculate or display dynamic content.Syntax
The basic syntax of a DIESEL expression in AutoCAD is %. The expression is enclosed between percent signs and can include functions, variables, and operators.
- %: Delimiters that mark the start and end of the DIESEL expression.
- expression: The code inside that performs calculations or returns values.
Example functions include getvar() to get system variables, if() for conditions, and arithmetic operators like +, -, *, and /.
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%getvar("ctab")%Output
Returns the name of the current tab (layout or model space).
Example
This example shows how to use a DIESEL expression to display the current layer name dynamically in a text field.
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%getvar("clayer")%Output
Displays the name of the current layer, e.g., "Layer1".
Common Pitfalls
Common mistakes when using DIESEL expressions include:
- Forgetting the percent signs
%around the expression, which causes it to display as plain text. - Using incorrect function names or syntax, which results in errors or no output.
- Not escaping quotes properly inside functions like
getvar("variable"). - Trying to use complex logic that DIESEL does not support; it is designed for simple expressions only.
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Wrong: getvar("clayer") Right: %getvar("clayer")%
Quick Reference
| Function | Description | Example |
|---|---|---|
| getvar("varname") | Returns the value of a system variable | %getvar("clayer")% |
| if(condition, true_result, false_result) | Returns true_result if condition is true, else false_result | %if(1=1,"Yes","No")% |
| strcat(str1, str2) | Concatenates two strings | %strcat("Layer: ", getvar("clayer"))% |
| Arithmetic operators | Perform math operations | %5+3% returns 8 |
Key Takeaways
Always enclose DIESEL expressions between percent signs % to activate them.
Use simple functions like getvar() and if() for dynamic text in AutoCAD.
Escape quotes inside functions properly to avoid errors.
DIESEL is for simple expressions; complex logic requires other methods.
Test expressions in text fields to verify correct output before use.