[Chapter 10] 10.3 Environment Variables

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| Chapter 10 Accessing the Environment |

## 10.3 Environment Variables

Java does not provide any way to directly access environment variables defined on a system. There is a `System.getEnv()` method that served that purpose before Java 1.0 was released. However, in released versions of Java, the `System.getEnv()` method just throws an exception with a message explaining that it is not supported.

However, an environment variable can be made available as a system property if it is defined as a system property on the command line that invokes the Java virtual machine. For example, to make the environment variable `PRINTER` available as a system property in a Windows environment, you can write:

    C:\> java -Dprinter=%PRINTER%

In a UNIX environment, you can use:

    % java -Dprinter=$PRINTER

System Properties |  | External Program Execution