read-char-no-hang

(read-char-no-hang &optional stream eof-error-p eof-value)

Reads one character from stream (default: standard input) if one is available without waiting, and returns it. On a stream HANDLE -- a file, a string input stream, a socket -- rontolisp answers exactly what read-char answers: no source it can open reports "a character would block" separately from "read one", and CL allows an implementation to say so. On a Gray stream instance it dispatches to rontolisp:stream-read-char-no-hang, which is the generic a class with a genuinely non-blocking source overrides; that generic's own default is stream-read-char. At end of input it signals an end-of-file condition unless eof-error-p is nil, in which case it returns eof-value (default nil).