> For the complete documentation index, see [llms.txt](https://documentation.hak5.org/hak5-usb-rubber-ducky/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://documentation.hak5.org/hak5-usb-rubber-ducky/advanced-features/conditional-compilation.md).

# Conditional Compilation

As covered in the [Constants section](/hak5-usb-rubber-ducky/attack-modes-constants-and-variables/constants.md), `DEFINE` can be used to declare constants used throughout your payloads. Using `DEFINE` and some additional commands described below we can gain even more control over the source code that get included into your `inject.bin`during compilation.

### What problem does this solve?

Imagine you have a payload that you would like to add some **optional** features to. With the help of a `DEFINE` you could provide a set of boolean constants to toggle those features on or off; consider the example below:

```
DEFINE #EnableExtraFeature1 TRUE
DEFINE #EnableExtraFeature2 FALSE
DEFINE #EnableExtraFeature3 FALSE

... payload ...

IF #EnableExtraFeature1 THEN
 ... code will always run ...
END_IF

IF #EnableExtraFeature2 THEN
 ... code will always get skipped at runtime ...
END_IF

IF #EnableExtraFeature3 THEN
 ... code that will always get skipped at runtime ...
END_IF

```

Here we have `#EnableExtraFeature1` set to `TRUE`. At the time of compile `IF #EnableExtraFeature1 THEN` will become `IF TRUE THEN` which will allow for the code within that `IF` statement to be executed. 

While the payload user is deciding to enable that feature *before* compiling their `inject.bin` by setting `#EnableExtraFeature1` to `TRUE`, the USB Rubber Ducky is still evaluating the `IF` statement **during runtime of the payload** even though we know `IF TRUE` will *always* evaluate to `TRUE`. 

In the opposite case, the features that are **disabled** are *still compiled into the `inject.bin` .* The USB Rubber Ducky still has to evaluate the `IF #EnabledExtraFeature3 THEN` which we know will become `IF FALSE THEN` to decide to skip the code within the `IF` statement. This becomes not only a waste of space but a waste of computation that could be better used. 

### Solution

Using `IF_DEFINED_TRUE` `IF_NOT_DEFINED_TRUE` and `ELSE_DEFINED`,we can conditionally include portions of our payload in the resulting `inject.bin`.

{% hint style="info" %}
These act similarly to `IF / ELSE` except they are evaluated **before** compile time and control *inclusion* or *exclusion* of blocks of code.
{% endhint %}

## IF\_DEFINED\_TRUE

With `IF_DEFINED_TRUE`, the code within it's body/block will be compiled into the `inject.bin` *ONLY* if the given `LABEL` **exists and evaluates to** `TRUE`

### Syntax

```
IF_DEFINED_TRUE #LABEL
    ... code ...
END_IF_DEFINED
```

### Example

```
DEFINE #EnableExtraFeature1 TRUE
DEFINE #EnableExtraFeature2 FALSE

... payload ...

IF_DEFINED_TRUE #EnableExtraFeature1
 ... code that will be included because #EnableExtraFeature1 is TRUE ...
END_IF_DEFINED

IF_DEFINED_TRUE #EnableExtraFeature2
 ... code that wont be included because #EnableExtraFeature2 is FALSE ...
END_IF_DEFINED

IF_DEFINED_TRUE #EnableExtraFeature3
 ... code that wont be included because #EnableExtraFeature3 does not exist ...
END_IF_DEFINED
```

## IF\_NOT\_DEFINED\_TRUE

As the opposite of `IF_DEFINED_TRUE`, with `IF_NOT_DEFINED_TRUE`, the code within it's body/block will be compiled into the `inject.bin` if the given `LABEL` **does not** **exist or evaluates to** `FALSE`

### Syntax

```
IF_NOT_DEFINED_TRUE #LABEL
    ... code ...
END_IF_DEFINED
```

### Example

```
DEFINE #EnableExtraFeature1 TRUE
DEFINE #EnableExtraFeature2 FALSE

... payload ...

IF_NOT_DEFINED_TRUE #EnableExtraFeature1
 ... code that wont be included because #EnableExtraFeature1 is TRUE ...
END_IF_DEFINED

IF_NOT_DEFINED_TRUE  #EnableExtraFeature2
 ... code that will be included because #EnableExtraFeature2 is FALSE ...
END_IF_DEFINED

IF_NOT_DEFINED_TRUE #EnableExtraFeature3
 ... code that will be included because #EnableExtraFeature3 does not exist ...
END_IF_DEFINED
```

## ELSE\_DEFINED

Used in combination with `IF_DEFINED_TRUE` and `IF_NOT_DEFINED_TRUE` to provide the alternative to the provided condition; the negated case. Code within the `ELSE_DEFINED` body/block will only be included if the paired `IF_DEFINED_TRUE` or `IF_NOT_DEFINED_TRUE` case **is not met**.

### Syntax

```
IF_DEFINED_TRUE #LABEL
    ... code ...
ELSE_DEFINED
    ... other code ...
END_IF_DEFINED
```

```
IF_NOT_DEFINED_TRUE #LABEL
    ... code ...
ELSE_DEFINED
    ... other code ...
END_IF_DEFINED
```

### Example

```
DEFINE #EnableExtraFeature1 TRUE
DEFINE #EnableExtraFeature2 FALSE

... payload ...

IF_NOT_DEFINED_TRUE #EnableExtraFeature1
 ...  code that wont be included because #EnableExtraFeature1 is TRUE ...
ELSE_DEFINED
 ... alternative to feature 1 that wont be included because #EnableExtraFeature1 is TRUE ...
END_IF_DEFINED

IF_NOT_DEFINED_TRUE  #EnableExtraFeature2
 ... code that will be included because #EnableExtraFeature2 is FALSE ...
END_IF_DEFINED

IF_NOT_DEFINED_TRUE #EnableExtraFeature3
 ... code that will be included because #EnableExtraFeature3 does not exist ...
END_IF_DEFINED
```