Returns the count of characters remaining after trying to write string to the output stream. The stream also advances the write pointer.

The string can be the null string. In this case, charOut writes no characters to the stream and returns 0. If you omit string, charOut writes no characters to the stream and returns 0. The stream is also closed.

If you specify start, this positions the write pointer before writing. If the stream is not already open, the stream attempts to open for reading and writing. If that fails, the stream opens for for output only.