close-input-port, close-output-port - close a port

(import (rnrs))                     ;R6RS
(import (rnrs io simple))           ;R6RS
(import (scheme r5rs))              ;R7RS
(import (scheme base))              ;R7RS

(close-input-port port)
(close-output-port port)

Closes the file associated with port, rendering the port incapable of delivering or accepting characters. These routines have no effect if the file has already been closed.

R6RS

If port is a custom port then the closer procedure is called before the port is really closed.

Custom ports have a single closer procedure, so they do not compose well with only closing one direction. R6RS does not explicitly make any mention of closing only one direction.

R7RS

Scheme implementations may provide ports which are simultaneously input and output ports, such as sockets; the close-input-port and close-output-port procedures can then be used to close the input and output sides of the port independently.

Returns unspecified values.

(define p (open-output-file "hello.txt"))
(display "Hello, world\n" p)
(close-output-port p)

Ports are often connected to some limited resource, such as a file descriptor. Closing ports is important to avoid resource leaks. Some implementations will garbage collect ports, but this is not required.

In R6RS these procedures are part of the "simple I/O" library, which is provided for compatibility with code written for R5RS and earlier reports.

These procedures are provided for portability with code written for R5RS and earlier reports.

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.

&i/o-write (R6RS)

There was buffered data in the port and a write error while the port was being flushed. This is applicable to combined input/output ports.

&i/o-port (R6RS)

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

It is an error to apply these procedures to a port which is not an input or output port, respectively.

close-port(3scm), call-with-port(3scm)

R4RS, IEEE Scheme, R5RS, R6RS, R7RS

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/.

It is often better to use call-with-port(3scm) or one of the related procedures. They make it easier to ensure that a port is closed when an exception is raised.