Java getenv() returns null

Question

I'm defining an environment variable in a Linux shell with TestEnviron=varproperty. Now, I want to write a small program that reads the environment variable, writes it to the console output, and writes the variable to a properties file. However when I try it with this code getenv() returns null:

package javaenvironmentvariable;

import java.io.File;
import java.io.FileOutputStream;
import java.util.Properties;

public class JavaEnvironmentVariable {
    public static void main(String[] args) {
        try {
            String variable = System.getenv("TestEnviron");
            System.out.println("TestEnviron: " + variable);
            variable = "TestEnviron=" + variable;

            Properties properties = new Properties();

            File file = new File("Variables.properties");
            FileOutputStream fileout = new FileOutputStream(file);
            properties.store(fileout, variable);
            fileout.close();
        } catch (Exception e) {
        }
    }
}

I use this in the shell to call the jar: sudo java -jar JavaEnvironmentVariable.jar

How did you define your variable in the shell ? Do you run your program right after defining it or in another shell ? How do you launch your program ? — perencia, Sep 13 '15 at 09:54
If you use another shell to launch your program use `export` to define your var: `export TestEnviron=varproperty` — aghidini, Sep 13 '15 at 09:54
@perencia I used TestEnviron=varproperty in the stell, and right after that i run my programm with this sudo java -jar JavaEnvironmentVariable.jar in the same shell. — nick bijmoer, Sep 13 '15 at 09:57
@nickbijmoer you get your variable if you do `env` in your shell ? — perencia, Sep 13 '15 at 10:01
Why use `sudo`? See [this question](http://stackoverflow.com/questions/8633461/how-to-keep-environment-variables-when-using-sudo) for more info on `sudo` and env vars. You can launch your program with `sudo -E` to keep your environment in sudo. — aghidini, Sep 13 '15 at 10:01
Reac what @AndreaGhidini told you. You missed the `export` part. — user207421, Sep 13 '15 at 10:05

score 4 · Accepted Answer · edited May 23 '17 at 12:23

4

You should use sudo -E AND export to keep the environment variables:

$ export TestEnviron=varproperty
$ sudo -E java -jar JavaEnvironmentVariable.jar

However to be more safe you should configure sudo to keep your variable as explained in this post: How to keep Environment Variables when Using SUDO :

sudo visudo

and add this line:

Defaults env_keep += "TestEnviron"

edited May 23 '17 at 12:23

Community

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answered Sep 13 '15 at 10:07

aghidini

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Yeah thats the solution! thanks a lot! I did not know that sudo wont keep the environment variables. – nick bijmoer Sep 13 '15 at 10:15

score 2 · Answer 2 · answered Sep 13 '15 at 09:55

2

Shells don't automatically put their variables into the environment. You need to explicitly export the variable using export ENVVAR=VALUE or set -x ENVVAR VALUE depending on your shell.

answered Sep 13 '15 at 09:55

Functino

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It didn't work because I used sudo apparently but thanks for the export tip :) – nick bijmoer Sep 13 '15 at 10:18

score 0 · Answer 3 · answered Sep 13 '15 at 09:55

0

I think your are setting the environment variable in one shell and executing your program in another shell. Try to execute both in a same shell. Before executing the program check by printing the environment variable in shell.

answered Sep 13 '15 at 09:55

Shriram

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I am executing them in the same shell but still get null, I printed the variable with this code: echo $TestEnviron and then it returns varproperty so thats fine. – nick bijmoer Sep 13 '15 at 10:03

Java getenv() returns null

3 Answers3