Question

I’m experimenting with a rooted Android tablet. I need to run some system applications in C/C++ that can run as native apps with/without using the NDK. This would work like existing command line applications such as toolbox as a native ARM Linux executable.
Is that a possibility?

Answer 1

Yes, you can. And you can do it using the NDK which you make things easier to you , cross-compiling to all platforms supported by Android (ARM variants and x86). You just need to do like you would do to create a shared library for native Java methods. Just make sure you change the makefile to use BUILD_EXECUTABLE instead of BUILD_SHARED_LIBRARY to create an executable. Of course you won’t need the APK folder structure, just the “jni” folder.

Tutorial

Create the project folders:

mkdir project_folder
cd project_folder/jni
NDK_PROJECT_PATH=<path to>/project_folder

Create the Android.mk makefile in the jni folder

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE    := teste
LOCAL_SRC_FILES := teste.c

include $(BUILD_EXECUTABLE)

Create also your source code in the jni. In this case, you can see from above makefile, it is teste.c:

#include <stdio.h>


int main (){

    puts("Hello World");
    return 0;
}

Now go up to your project folder and run ndk-build from there:

# ~/Downloads/android-ndk-r8b/ndk-build 
Compile thumb  : teste <= teste.c
Executable     : teste
Install        : teste => libs/armeabi/teste

Although it is output to a lib folder it is a executable, as you can inspect with file

#file libs/armeabi/teste 
libs/armeabi/teste: ELF 32-bit LSB executable, ARM, version 1 (SYSV), dynamically linked (uses shared libs), stripped