read-char &optional input-stream eof-error-p eof-value recursive-p ⇒ char
| 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_2 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
*standard-input*, *terminal-io*.
If an end of file_2 occurs before a character can be read, and eof-error-p is true, an error of type end-of-file is signaled.
The corresponding output function is write-char.