►The Racket Reference
►12 Input and Output
▼12.1 Ports
On this page:
input-port?
output-port?
port?
close-input-port
close-output-port
port-closed?
port-closed-evt
current-input-port
current-output-port
current-error-port
file-stream-port?
terminal-port?
eof
eof-object?
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12.1.2 Managing Ports

procedure

(input-port? v) → boolean?

  v : any/c
Returns #t if v is an input port, #f otherwise.

procedure

(output-port? v) → boolean?

  v : any/c
Returns #t if v is an output port, #f otherwise.

procedure

(port? v) → boolean?

  v : any/c
Returns #t if either (input-port? v) or (output-port? v) is #t, #f otherwise.

procedure

(close-input-port in) → void?

  in : input-port?
Closes the input port in. For some kinds of ports, closing the port releases lower-level resources, such as a file handle. If the port is already closed, close-input-port has no effect.

procedure

(close-output-port out) → void?

  out : output-port?
Closes the output port out. For some kinds of ports, closing the port releases lower-level resources, such as a file handle. Also, if the port is buffered, closing may first flush the port before closing it, and this flushing process can block. If the port is already closed, close-output-port has no effect.

procedure

(port-closed? port) → boolean?

  port : port?
Returns #t if the input or output port port is closed, #f otherwise.

procedure

(port-closed-evt port) → evt?

  port : port?
Return a synchronizable event that becomes ready when port is closed.

parameter

(current-input-port) → input-port?

(current-input-port in) → void?
  in : input-port?
A parameter that determines a default input port for many operations, such as read.

parameter

(current-output-port) → output-port?

(current-output-port out) → void?
  out : output-port?
A parameter that determines a default output port for many operations, such as write.

parameter

(current-error-port) → output-port?

(current-error-port out) → void?
  out : output-port?
A parameter that determines an output port that is typically used for errors and logging. For example, the default error display handler writes to this port.

procedure

(file-stream-port? port) → boolean?

  port : port?
Returns #t if the given port is a file-stream port (see File Ports), #f otherwise.

procedure

(terminal-port? port) → boolean?

  port : port?
Returns #t if the given port is attached to an interactive terminal, #f otherwise.

value

eof : eof-object?

A value (distinct from all other values) that represents an end-of-file.

procedure

(eof-object? a) → boolean?

  a : any/c
Returns #t if v is eof, #f otherwise.

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