How to use standard output streams for logging in android apps


Android applications are strange beasts. Even though under the hood it’s basically a UNIX system using Linux as its kernel, there are other layers between (native) android apps and the bare system, that some things are bound to fall through the cracks.

When developing android apps, one generally doesn’t login to the actual device to compile and execute the program; instead a cross-compiler is provided by google, along with a series of tools to package, install, and execute the app. The degrees of separation from the actual controlling terminal of the application, make it harder to just print debugging messages to the stdout and stderr streams and watch the output like one could do while hacking a regular program. For this reason, the android NDK provides a set of logging functions, which append the messages to a global log buffer. The log buffer can be viewed and followed remotely, from the development machine, over USB, by using the “adb logcat” tool.

This is all well and good, but if you’re porting a program which prints a lot of messages to stdout/stderr, or if you just like the convenience of using the standard printf/cout/etc functions, instead of funny looking stuff like __android_log_print(), you might wonder if there is a way to just use the standard I/O streams instead, right? Well so did I, and guess what… this is still UNIX so the answer is of course you can!

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