---
title: "Control your system settings with environment variables"
canonical: "https://support.appfire.com/space/PSJ/15486473/Control%20your%20system%20settings%20with%20environment%20variables"
format: markdown
---
> Macro (aura-html)


> Macro (excerpt)
> 
> In addition to the local variables defined in a SIL™ program and issue variables (Variable Resolution), there are environment variables. These are global constants you can access in any SIL™ program using the silEnv function.

In addition to the local variables defined in a SIL™ program and issue variables ([Variable Resolution](https://appfire.atlassian.net/wiki/spaces/PSJ/pages/15485601)), there are environment variables. These are global constants you can access in any SIL™ program using the [silEnv](https://appfire.atlassian.net/wiki/spaces/PSJ/pages/15489714) function.

# Declaring Environment Variables

To be able to use these variables, you have to follow two steps:

1. Environment variables must be defined in a special file named sil.properties. This file is placed in the same directory designated as sil.home (for instance the one that contains all your scripts). You must create this file manually.

##### **sil.properties**

```
VAT=0.24
```

2. Retrieve the value in the SIL™ program and then use it just like any other variable. Make sure you cast it to your designated type (in our case, a number).

```
number VAT = silEnv("VAT");
number price = customfield_10019;
print("VAT is:" + (price * VAT));
```