get-bytevector-n, read-bytevector - read data from a binary port

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

;; R6RS
(get-bytevector-n binary-input-port k)
;; R7RS
(read-bytevector k)
(read-bytevector k binary-input-port)

Reads from binary-input-port, blocking as necessary, until count bytes are available from binary-input-port or until an end of file is reached. If an end of file is reached before any bytes are available then the end-of-file object is returned. The input port is updated to point just past the bytes read.

R7RS

The default value for binary-input-port is the object returned by current-input-port(3scm).

Multiple end-of-file conditions

The port may return an end-of-file object and then still keep producing data if another read is attempted. Files do not normally work this way, but it is possible for other types of ports to do so, such as terminals. R6RS explicitly mentions this situation while R7RS does not.

Returns a single value; a bytevector or an end-of-file object. An empty bytevector is returned if k is zero.

R6RS

There is a single, unique end-of-file object.

(call-with-port (open-file-input-port "/dev/zero")
  (lambda (p)
    (get-bytevector-n p 4)))
        => #vu8(0 0 0 0)

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, count must be an exact, nonnegative integer object, and binary-input-port must be an open binary input port.

&i/o-read (R6RS)

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

&i/o-port (R6RS)

This condition specifies the port object related to an &i/o-read condition.

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.

eof-object?(3scm), get-bytevector-some(3scm), get-bytevector-all(3scm), get-bytevector-n!(3scm)

R6RS, R7RS

Reports prior to R6RS did not support binary I/O.

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/.

The default port used by read-bytevector is the current input port, which is normally a textual port that is not expected to support binary I/O.