Environment variables inheritance behaviour

Question

The following code snippet is provided:

public static void main(String[] args) throws InterruptedException {
    Map<String, String> env = System.getenv();
    for (String envName : env.keySet()) {
        System.out.format("%s=%s%n", envName, env.get(envName));
    }
}

Run/Debug configuration in IDEA looks like:

When this snipped is executed with "Include parent environment variables" checkbox on, all env vars are printed as expected, however if unset this checkbox only SystemRoot var is printed.

I've not noticed any difference between program exec command:

"C:\Program Files\Java\jdk1.8.0_152\bin\java" -Dvisualvm.id=2058947361732085 "-javaagent:C:\Program Files\JetBrains\IntelliJ IDEA 2017.3\lib\idea_rt.jar=3099:C:\Program Files\JetBrains\IntelliJ IDEA 2017.3\bin" -Dfile.encoding=UTF-8 -classpath "C:\Program Files\Java\jdk1.8.0_152\jre\lib\charsets.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\deploy.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\ext\access-bridge-64.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\ext\cldrdata.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\ext\dnsns.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\ext\jaccess.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\ext\jfxrt.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\ext\localedata.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\ext\nashorn.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\ext\sunec.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\ext\sunjce_provider.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\ext\sunmscapi.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\ext\sunpkcs11.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\ext\zipfs.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\javaws.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\jce.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\jfr.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\jfxswt.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\jsse.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\management-agent.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\plugin.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\resources.jar;C:\Program Files\Java\jdk1.8.0_152\jre\lib\rt.jar;D:\Projects\untitled\out\production\untitled" com.myapp.Main

How does application know whether to inherit parent env variables or not?

How I configure such behaviour while running an app from command line?

Answer 1

When running an application inside IntelliJ there are 2 Java processes/VMs

1. The VM used to run IntelliJ
2. The VM used to run your application

(1) is considered to be the parent of (2). When launching your application from inside IntelliJ you can use the aforementioned checkbox to pass any environment variables of (1) to (2).

This doesn't apply when running an app directly from the command line, because there's only a single Java process/VM.