1 Language Model
2 Syntactic Forms
3 Datatypes
4 Structures
5 Classes and Objects
6 Units
7 Contracts
8 Pattern Matching
9 Control Flow
10 Concurrency
11 Macros
12 Input and Output
13 Reflection and Security
14 Operating System
15 Memory Management
16 Running PLT Scheme
Bibliography
Index
On this page:
input-port?
output-port?
port?
close-input-port
close-output-port
port-closed?
current-input-port
current-output-port
current-error-port
file-stream-port?
terminal-port?
eof
eof-object?
Version: 4.0.1

 

12.1.2 Managing Ports

(input-port? v)  boolean?

  v : any/c

Returns #t if v is an input port, #f otherwise.

(output-port? v)  boolean?

  v : any/c

Returns #t if v is an output port, #f otherwise.

(port? v)  boolean?

  v : any/c

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

(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.

(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.

(port-closed? port)  boolean?

  port : port?

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

(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.

(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.

(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.

(file-stream-port? port)  boolean?

  port : port?

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

(terminal-port? port)  boolean?

  port : port?

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

eof : eof-object?

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

(eof-object? a)  boolean?

  a : any/c

Returns #t is v is eof, #f otherwise.