gOutputStreamWrite(object, buffer, cancellable = NULL, .errwarn = TRUE)
gOutputStreamWriteAll(object, buffer, bytes.written, cancellable = NULL, .errwarn = TRUE)
gOutputStreamSplice(object, source, flags = "G_OUTPUT_STREAM_SPLICE_NONE", cancellable = NULL, .errwarn = TRUE)
gOutputStreamFlush(object, cancellable = NULL, .errwarn = TRUE)
gOutputStreamClose(object, cancellable = NULL, .errwarn = TRUE)
gOutputStreamWriteAsync(object, buffer, io.priority = 0, cancellable = NULL, callback, user.data = NULL)
gOutputStreamWriteFinish(object, result, .errwarn = TRUE)
gOutputStreamSpliceAsync(object, source, flags = "G_OUTPUT_STREAM_SPLICE_NONE", io.priority = 0, cancellable = NULL, callback, user.data = NULL)
gOutputStreamSpliceFinish(object, result, .errwarn = TRUE)
gOutputStreamFlushAsync(object, io.priority = 0, cancellable = NULL, callback, user.data = NULL)
gOutputStreamFlushFinish(object, result, .errwarn = TRUE)
gOutputStreamCloseAsync(object, io.priority = 0, cancellable = NULL, callback, user.data = NULL)
gOutputStreamCloseFinish(object, result, .errwarn = TRUE)
gOutputStreamIsClosed(object)
gOutputStreamHasPending(object)
gOutputStreamSetPending(object, .errwarn = TRUE)
gOutputStreamClearPending(object) 
GFlags
   +----GOutputStreamSpliceFlags
GObject
   +----GOutputStream
         +----GFilterOutputStream
         +----GFileOutputStream
         +----GMemoryOutputStream
         +----GUnixOutputStream
gOutputStreamWrite),
to close a stream (gOutputStreamClose) and to flush pending writes
(gOutputStreamFlush). To copy the content of an input stream to an output stream without 
manually handling the reads and writes, use gOutputStreamSplice. All of these functions have async variants too.