Why are there fileDescriptor modes (r,w,rw) and what are they for?

   contentResolver.openFileDescriptor(uri, "w")

They are described in the documention like this:

If opening with the exclusive "r" or "w" modes, the returned ParcelFileDescriptor could be a pipe or socket pair to enable streaming of data. Opening with the "rw" mode implies a file on disk that supports seeking. If possible, always use an exclusive mode to give the underlying ContentProvider the most flexibility.

CodePudding user response：

These are nothing but modes in which you can open file descriptor.

• "r" Read only mode. cannot be used for writing
• "w" Write only mode. cannot be used for reading.
• "rw" for read-and-write.
• "rwt" for truncating or overwriting existing file contents.