How to get "printf" messages written in NDK application?

use __android_log_print() instead. You have to include header <android/log.h>

Sample Example. __android_log_print(ANDROID_LOG_DEBUG, "LOG_TAG", "\n this is log messge \n");

You can also use format specifier like printf -

__android_log_print(ANDROID_LOG_DEBUG, "LOG_TAG", "Need to print : %d %s",int_var, str_var);

Make sure you also link against the logging library, in your Android.mk file:

  LOCAL_LDLIBS := -llog

Ohh.. forgot .. The output will be shown in Logcat with tag LOG_TAG

Easy Approach

Add the following lines to your common header file.

#include <android/log.h>#define  LOG_TAG    "your-log-tag"#define  LOGD(...)  __android_log_print(ANDROID_LOG_DEBUG, LOG_TAG, __VA_ARGS__)#define  LOGE(...)  __android_log_print(ANDROID_LOG_ERROR, LOG_TAG, __VA_ARGS__)// If you want you can add other log definition for info, warning etc

Now just call LOGD("Hello world") or LOGE("Number = %d", any_int) like printf in c.

Don't forget to include the common header file.

Remove the logging

If you define LOGD(...) empty, all logs will be gone. Just comment after LOGD(...).

#define LOGD(...) // __android_log..... rest of the code

There is two options:

1) replace printf with __android_log_print. You can do this easily with define at beginning of code:

#define printf(...) __android_log_print(ANDROID_LOG_DEBUG, "TAG", __VA_ARGS__);

Of course this will require changing all source code that has printf.

2) redirect stdout and stderr to Android logcat (not sure if this will work on non-rooted device): http://developer.android.com/guide/developing/debugging/debugging-log.html#viewingStd

not need to root device, acroding to http://developer.android.com/guide/developing/debugging/debugging-log.html#viewingStd, below can work prefectly.

$ adb shell $ su $ stop$ setprop log.redirect-stdio true$ start

done!