Run native executable in Android App

Demo †

Here‘s demo application called "Run Native Exe" to:

• run local UNIX commands
• run native executable downloaded from the Web

Package: NativeExe-0.2.apk
Source code: on Github (ADT project)

To install the package,

• Go to Settings→Application and check "Unknown sources"
• Open the package link above using Android Browser

or type "adb install NativeExe-*.apk" in your PC if you have Android SDK.

How can I run UNIX commands in Android App? †

You can use Runtime.exec() in standard Java. Here‘s sample code to run /system/bin/ls /sdcard in Android App:

try {
    // Executes the command.
    Process process = Runtime.getRuntime().exec("/system/bin/ls /sdcard");
    
    // Reads stdout.
    // NOTE: You can write to stdin of the command using
    //       process.getOutputStream().
    BufferedReader reader = new BufferedReader(
            new InputStreamReader(process.getInputStream()));
    int read;
    char[] buffer = new char[4096];
    StringBuffer output = new StringBuffer();
    while ((read = reader.read(buffer)) > 0) {
        output.append(buffer, 0, read);
    }
    reader.close();
    
    // Waits for the command to finish.
    process.waitFor();
    
    return output.toString();
} catch (IOException e) {
    throw new RuntimeException(e);
} catch (InterruptedException e) {
    throw new RuntimeException(e);
}

This code is based on this article. Thanks yussi to let me know this by comment.

OK, but how can I put my own native executable in Android App? †

First, you need to cross-compile your native executable for ARM.

Here‘s a way (dynamic link version). Or you can use Scratchbox (Japanese).

If you get a file with a format like this, it‘s probably OK:

% file yourapp
yourapp: ELF 32-bit LSB executable, ARM, version 1 (SYSV), for GNU/Linux 2.6.14, statically linked, not stripped

You have three ways to put the binary to the phone:

• From Android Java app, using assets folder (by fnerg in comment below)
  • Include the binary in the assets folder.
  • Use getAssets().open("YourBinaryHere") to get an InputStream.
  • Write it to /data/data/app-package-name (e.g. /data/data/net.gimite.nativeexe), where your application has access to write files and make it executable.
  • Run "/system/bin/chmod 744 /data/data/app-package-name/yourapp" using the code above.
  • Run your executable using the code above.

• From Android Java app, downloading via HTTP (which I use in my demo application above)
  • Dowload the executable using HTTP and put it to /data/data/app-package-name (e.g. /data/data/net.gimite.nativeexe), where your application has access to write files and make it executable. You can use standard Java FileOutputStream to write files there.
  • Run "/system/bin/chmod 744 /data/data/app-package-name/yourapp" using the code above.
  • Run your executable using the code above.

• By adb (needs SDK and root)
  • If you want to put the executable to YOUR phone connected with adb command in Android SDK and you have root, you can put the executable by:

% adb shell
$ su
# mkdir /data/tmp
# chmod 777 /data/tmp
# exit
$ exit
% adb push yourapp /data/tmp
% adb shell
$ chmod 744 /data/tmp/yourapp
$ /data/tmp/yourapp

Note that you cannot make files executable in /sdcard.