optional GCancellable object, NULL to ignore. [allow-none]
a string with the line that was read in (without the newlines). Set length to a gsize to get the length of the read line. On an error, it will return NULL and error will be set. If there's no content to read, it will still return NULL, but error won't be set. [transfer full]
GException on failure.
Reads a line from the data input stream. If cancellable is not NULL, then the operation can be cancelled by triggering the cancellable object from another thread. If the operation was cancelled, the error G_IO_ERROR_CANCELLED will be returned.