Removable Storage Access in Android with NDK API

Question

My question should be kinda simple but I search a lot from the internet, cannot find the answer.

I could get the path of secondary removable storage(sdcard) with below code

String ExternalSdcardPath = System.getenv("SECONDARY_STORAGE") + "/Sample/";

and I could get path like this , /storage/external_SD/Sample/

and I tried to create file with NDK API ( fopen(ExternalSdcardPath, "a+"); )

but I couldn't create and read file with fopen..

can you please tell me how to create and read file with fopen api in removable path(secondary_storage) ?

Answer 1

I could get the path of secondary removable storage(sdcard) with below code

There is no requirement for that environment variable to exist, let alone point to something meaningful.

I couldn't create and read file with fopen

You do not have direct filesystem access to arbitrary locations on removable storage on Android 4.4+.

can you please tell me how to create and read file with fopen api in removable path(secondary_storage) ?

Your only places for direct filesystem access to removable storage is in the locations returned by getExternalFilesDirs() , getExternalCacheDirs() , and getExternalMediaDirs() . Those are all methods on Context (eg, an activity or service). If they return 2+ values, the second and subsequent ones are on removable storage. Your Java code can supply those paths to your NDK code.