System.getenv() Method - System Environment Variables

Android Tutorials - Herong's Tutorial Examples

∟AboutAndroid - Application to Retrieve System Information

∟System.getenv() Method - System Environment Variables

This section provides tutorial example on how to display system environment variables using the java.lang.System.getenv() method.

With the ScrollView working, I can display more information about the system now with java.lang.System.getenv() method:

1. Enhance my application to display environment variables editing .\src\com\herongyang\AboutAndroid.java

/* AboutAndroid.java
 * Version 4.0 - Adding environment variables
 * Copyright (c) 2015, HerongYang.com, All Rights Reserved.
 */
package com.herongyang;

import android.app.Activity;
import android.os.Bundle;
import android.widget.TextView;
import android.widget.ScrollView;
public class AboutAndroid extends Activity {
   @Override
   public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      String msg = "";

      msg += "System properties\n";
      msg += "-------------\n";
      java.util.Properties props = System.getProperties();
      java.util.Enumeration e = props.propertyNames();
      while (e.hasMoreElements()) {
         String k = (String) e.nextElement();
         String v = props.getProperty(k);
         msg += k+": "+v+"\n";
      }

      msg += "\n";
      msg += "Environment variables\n";
      msg += "-------------\n";
      java.util.Map envs = System.getenv();
      java.util.Set keys = envs.keySet();
      java.util.Iterator i = keys.iterator();
      while (i.hasNext()) {
         String k = (String) i.next();
         String v = (String) envs.get(k);
         msg += k+": "+v+"\n";
      }

      TextView tv = new TextView(this);
      tv.setText(msg);
      ScrollView sv = new ScrollView(this);
      sv.addView(tv);
      setContentView(sv);
   }
}

2. Uninstall the previous version, build, install and run this new version. Environment variables are displayed after system properties.

Some interesting environment variables on my Android emulator are:

ANDROID_ASSETS: /system/app
ANDROID_DATA: /data
ANDROID_ROOT: /system
ASEC_MOUNTPOINT: /mnt/asec
BOOTCLASSPATH: /system/framework/core.jar:/system/framework/core-...
EXTERNAL_STORAGE: /storage/sdcard
LOOP_MOUNTPOINT: /mnt/obb
PATH: /sbin:/vendor/bin:/system/sbin:/system/bin:/system/xbin

Below was some system properties I got from my Android 4.0.3 emulator created with Android SDK R17:

ANDROID_ASSETS: /system/app
ANDROID_DATA: /data
ANDROID_ROOT: /system
ASEC_MOUNTPOINT: /mnt/asec
BOOTCLASSPATH: /system/framework/core.jar:/system/framework/core-...
EXTERNAL_STORAGE: /mnt/sdcard
LD_LIBRARY_PATH: /vendor/lib:/system/lib
LOOP_MOUNTPOINT: /mnt/obb
PATH: /sbin:/vendor/bin:/system/sbin:/system/bin:/system/xbin