21.2.14 read-byte [Function]

read-byte stream &optional eof-error-p eof-value ⇒ byte

Arguments and Values::

stream—a binary input stream.

eof-error-p—a generalized boolean. The default is true.

eof-value—an object. The default is nil.

byte—an integer, or the eof-value.

Description::

read-byte reads and returns one byte from stream.

If an end of file_2 occurs and eof-error-p is false, the eof-value is returned.

Examples::

 (with-open-file (s "temp-bytes" 
                     :direction :output
                     :element-type 'unsigned-byte)
    (write-byte 101 s)) ⇒  101
 (with-open-file (s "temp-bytes" :element-type 'unsigned-byte)
    (format t "~S ~S" (read-byte s) (read-byte s nil 'eof)))
 |>  101 EOF
⇒  NIL

Side Effects::

Modifies stream.

Exceptional Situations::

Should signal an error of type type-error if stream is not a stream.

Should signal an error of type error if stream is not a binary input stream.

If there are no bytes remaining in the stream and eof-error-p is true, an error of type end-of-file is signaled.

See Also::

read-char ,

read-sequence ,

write-byte