Location to store a pointer to a string holding the remaining data in the #GIOChannel. This data should be freed with g_free() when no longer needed. This data is terminated by an extra nul character, but there may be other nuls in the intervening data.
%G_IO_STATUS_NORMAL on success. This function never returns %G_IO_STATUS_EOF.
GException on failure.
Reads all the remaining data from the file.