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write-byte

write-byte Function

Syntax:

write-byte byte stream → byte

Arguments and Values:

byte—an integer of the stream element type of stream.

stream—a binary output stream.

Description:

write-byte writes one byte, byte, to stream.

Examples:

(with-open-file (s "temp-bytes" 
		   :direction :output 
		   :element-type ’unsigned-byte) 
  (write-byte 101 s)) → 101

Side Effects:

stream is modified.

Affected By:

The element type of the 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 output stream.

Might signal an error of type type-error if byte is not an integer of the stream element type of stream.

See Also:

read-byte, write-char, write-sequence

peek-char

Expanded Reference: write-byte​

Basic Usage​

write-byte writes one byte (an integer) to a binary output stream and returns the byte written.

(with-open-file (s "/tmp/cl-wb-test.bin"
                   :direction :output
                   :element-type '(unsigned-byte 8)
                   :if-exists :supersede)
  (write-byte 101 s))
=> 101

Writing Multiple Bytes​

(with-open-file (s "/tmp/cl-wb-test.bin"
                   :direction :output
                   :element-type '(unsigned-byte 8)
                   :if-exists :supersede)
  (dolist (b '(72 101 108 108 111))
    (write-byte b s)))
=> NIL

Round-Trip with read-byte​

Data written with write-byte can be read back with read-byte.

(with-open-file (out "/tmp/cl-wb-rt.bin"
                     :direction :output
                     :element-type '(unsigned-byte 8)
                     :if-exists :supersede)
  (write-byte 255 out)
  (write-byte 0 out)
  (write-byte 128 out))

(with-open-file (in "/tmp/cl-wb-rt.bin"
                    :element-type '(unsigned-byte 8))
  (list (read-byte in) (read-byte in) (read-byte in)))
=> (255 0 128)