put-u8, write-u8 - write a byte to a binary output port

(import (rnrs))                     ;R6RS
(import (rnrs io ports))            ;R6RS
(import (scheme base))              ;R7RS

(put-u8 binary-output-port byte)    ;R6RS
(write-u8 byte)                     ;R7RS
(write-u8 byte binary-output-port)  ;R7RS

Writes the byte to the given binary-output-port.

;; R7RS code to create a file with the single line "A"
(call-with-port (open-output-file "test.txt")
 (lambda (p)
   (write-u8 65 p)
   (write-u8 10 p)))

Commonly used in applications that create binary files or other binary data. There is often a mix of single bytes intermixed with larger writes with put-bytevector(3scm).

This procedure can raise exceptions with the following condition types:

&assertion (R6RS)

The wrong number of arguments was passed or an argument was outside its domain. In particular, byte must be an exact integer between 0 and 255.

&i/o-write (R6RS)

There was an I/O error during the write operation.

&i/o-port (R6RS)

If this is included as part of an I/O condition then the port related to the I/O error can be retrieved with i/o-error-port(3scm).

R7RS

The assertions described above are errors. Implementations may signal an error, extend the procedure's domain of definition to include such arguments, or fail catastrophically.

put-char(3scm), put-bytevector(3scm)

R6RS, R7RS

The put-u8 procedure is new to the reworked I/O system introduced with R6RS. The write-u8 procedure is new in R7RS and is similar to write-char(3scm) but works with binary output ports, which did not exist in R5RS.

This page is part of the scheme-manpages project. It includes materials from the RnRS documents. More information can be found at https://weinholt.se/scheme/manpages/.