How to compile C into an executable binary file and run it in Android from Android Shell?

Solution 1:

First, let me say that my answer is dependent on your using NDK r7b (it'll work for r7c as well) on Linux (change paths appropriately for other systems).

Edit: Last tested with NDK r8e on Linux and Nexus 4 with adb from SDK Platform-Tools Rev 18 on Windows 7 (latest as of 2013-07-25) without root access.

Yet Another Edit: Please read this question for altering my instruction for native binaries that need to run on Android 5.0(Lollypop) and later.

1. Go to $NDK_ROOT (The topmost folder of NDK zip when unzipped).
2. Copy $NDK_ROOT/samples/hello-jni directory as $NDK_ROOT/sources/hello-world.
3. Go to $NDK_ROOT/sources/hello-world.
4. Edit AndroidManifest.xml to give the application an appropriate name (This is optional).
5. Go to $NDK_ROOT/sources/hello-world/jni. This is where the source code is.
6. Edit hello-jni.c, remove all the code, and put in your hello world code. Mine is:

   #include 
   int main( int argc, char* argv[])
   {
       printf("Hello, World!");
       return 0;
   }

7. Edit Android.mk and change the line include $(BUILD_SHARED_LIBRARY) to include $(BUILD_EXECUTABLE). You can also change the LOCAL_MODULE line to the name you want for your executable(default is hello-jni)
8. Go back to $NDK_ROOT/sources/hello-world
9. Run ../../ndk-build to create the executable.
10. Copy it from $NDK_ROOT/sources/hello-jni/libs/armeabi/hello-jni to /data/local/tmp on the Android device and change it's permissions to 755 (rwxr-xr-x). If you changed the LOCAL_MODULE line in $NDK_ROOT/sources/hello-world/jni/Android.mk, the executable name will be the new value of LOCAL_MODULE instead of hello-jni. (All this is done via adb from the Android SDK.)
11. Execute the binary with full path as /data/local/tmp/hello-jni, or whatever you named it to.

And you're done( and free to start on the documentation in $NDK_ROOT/docs to get a better idea of what to do).

Solution 2:

The best/easiest place to put a executable is /data/local. You'll also need to chmod the binary as executable. Often you'll also need to do this in two steps to get the binary from /sdcard/ to /data/local:

$ adb push mybin /sdcard/
$ adb shell
$ cp /sdcard/mybin /data/local/mybin
$ cd /data/local
$ chmod 751 mybin

Caveats:

• Not all systems have cp. You can use cat if this is the case:

  $ cat /sdcard/mybin > /data/local/mybin

• Some systems don't allow write in /data/local for the "shell" user. Try /data/local/tmp