a >>= b will pass the result of
a to the
b function. This is a monadic
val return : 'a -> 'a t
return a will construct a constant IO value.
read_line ic will read a single line terminated by CR or CRLF from the input channel
ic. It returns
None if EOF or other error condition is reached.
read ic len will block until a maximum of
len characters are read from the input channel
ic. It returns an empty string if EOF or some other error condition occurs on the input channel, and can also return fewer than
len characters if input buffering is not sufficient to satisfy the request.
write oc s will block until the complete
s string is written to the output channel