char-ready?

(char-ready? [port])

Returns #t if a character can be read from the current input port without blocking. It always returns #t: with data waiting and at end of input that is the R7RS answer, but on a terminal where nothing has been typed yet it is also #t, and the next read then waits. With port, it asks about that port, which must be an open textual input port; the answer is #t there too.