read-char &optional input-stream eof-error-p eof-value recursive-p => char
Arguments and Values:
input-stream---an input stream designator. The default is standard input.
eof-error-p---a generalized boolean. The default is true.
eof-value---an object. The default is nil.
recursive-p---a generalized boolean. The default is false.
char---a character or the eof-value.
read-char returns the next character from input-stream.
When input-stream is an echo stream, the character is echoed on input-stream the first time the character is seen. Characters that are not echoed by read-char are those that were put there by unread-char and hence are assumed to have been echoed already by a previous call to read-char.
If recursive-p is true, this call is expected to be embedded in a higher-level call to read or a similar function used by the Lisp reader.
If an end of file occurs and eof-error-p is false, eof-value is returned.
(with-input-from-string (is "0123") (do ((c (read-char is) (read-char is nil 'the-end))) ((not (characterp c))) (format t "~S " c))) >> #\0 #\1 #\2 #\3 => NIL
If an end of file occurs before a character can be read, and eof-error-p is true, an error of type end-of-file is signaled.
read-byte, read-sequence, write-char, read
The corresponding output function is write-char.