hdl returns the list of characters
corresponding to the unread portion of the channel or file managed
hdl, which is put into an intermediate state, semi-closed.
In this state,
hdl is effectively closed,
but items are read from
hdl on demand and accumulated in a special
list returned by
Any operation that fails because a handle is closed, also fails if a handle is semi-closed. The only exception is hClose. A semi-closed handle becomes closed:
- if hClose is applied to it;
- if an I/O error occurs when reading an item from the handle;
- or once the entire contents of the handle has been read.
Once a semi-closed handle becomes closed, the contents of the associated list becomes fixed. The contents of this final list is only partially specified: it will contain at least all the items of the stream that were evaluated prior to the handle becoming closed.
Any I/O errors encountered while a handle is semi-closed are simply discarded.
This operation may fail with:
isEOFErrorif the end of file has been reached.