How to get around java.lang.UnsupportedOperationException: Can't modify environment?

Question

I'm trying to run a sub process on Android (see this question) which requires that the PYTHONHOME environment variable be set. I tried to do so with the following code:

    ProcessBuilder pbuilder = new ProcessBuilder("python/bin/python", "test.py");
    pbuilder.directory(getFilesDir());
    Map<String, String> env = pbuilder.environment();
    env.put("PYTHONHOME", "python");

    Process process = pbuilder.start();

but I get this exception:

E/AndroidRuntime(25857): FATAL EXCEPTION: main
E/AndroidRuntime(25857): java.lang.UnsupportedOperationException: Can't modify environment
E/AndroidRuntime(25857):    at java.lang.SystemEnvironment.put(System.java:740)
E/AndroidRuntime(25857):    at java.lang.SystemEnvironment.put(System.java:688)
E/AndroidRuntime(25857):    at my code
E/AndroidRuntime(25857):    at android.view.View.performClick(View.java:2408)
E/AndroidRuntime(25857):    at android.view.View$PerformClick.run(View.java:8816)
E/AndroidRuntime(25857):    at android.os.Handler.handleCallback(Handler.java:587)
E/AndroidRuntime(25857):    at android.os.Handler.dispatchMessage(Handler.java:92)
E/AndroidRuntime(25857):    at android.os.Looper.loop(Looper.java:123)
E/AndroidRuntime(25857):    at android.app.ActivityThread.main(ActivityThread.java:4627)
E/AndroidRuntime(25857):    at java.lang.reflect.Method.invokeNative(Native Method)
E/AndroidRuntime(25857):    at java.lang.reflect.Method.invoke(Method.java:521)
E/AndroidRuntime(25857):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
E/AndroidRuntime(25857):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
E/AndroidRuntime(25857):    at dalvik.system.NativeStart.main(Native Method)

Does anyone have any advice? I've tried wrapping the call to python in a shell script which exports PYTHONHOME but that didn't do the trick.

Gabe

Answer 1

Just recently ran into the same problem. Seems like you can't modify the ProcessBuilder's environment map on Android versions <= 2.2. The only workaround that I found was to use exec() rather than the ProcessBuilder. In your case, this would result in something along the lines of:

String[] cmdarray = {"python/bin/python", "test.py"};
String[] envp = {"PYTHONHOME=python"};
Process process = Runtime.getRuntime().exec(cmdarray, envp, getFilesDir());

Hope that helps.
C