12.1.7 Pipes

► |  | The Racket Reference

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 and Parallelism
11 | Macros
12 | Input and Output
13 | Reflection and Security
14 | Operating System
15 | Memory Management
16 | Unsafe Operations
17 | Running Racket
| Bibliography
| Index

► | 12 | Input and Output

12.1 | Ports
12.2 | Byte and String Input
12.3 | Byte and String Output
12.4 | Reading
12.5 | Writing
12.6 | Pretty Printing
12.7 | Reader Extension
12.8 | Printer Extension
12.9 | Serialization
12.10 | Fast-Load Serialization

▼ | 12.1 | Ports

12.1.1 | Encodings and Locales
12.1.2 | Managing Ports
12.1.3 | Port Buffers and Positions
12.1.4 | Counting Positions, Lines, and Columns
12.1.5 | File Ports
12.1.6 | String Ports
12.1.7 | Pipes
12.1.8 | Structures as Ports
12.1.9 | Custom Ports
12.1.10 | More Port Constructors, Procedures, and Events

On this page:

make-pipe
pipe-content-length

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##### 12.1.7`` Pipes

A Racket pipe is internal to Racket, and not related to OS-level pipes for communicating between different processes.OS-level pipes may be created by subprocess, opening an existing named file on a Unix filesystem, or starting Racket with pipes for its original input, output, or error port. Such pipes are file-stream ports, unlike the pipes produced by make-pipe.

> procedure (make-pipe [limit input-name output-name])
> | → |  |
> input-port? |  | output-port?
> limit : exact-positive-integer? = #f
> input-name : any/c = 'pipe
> output-name : any/c = 'pipe

Returns two port values: the first port is an input port and the second is an output port. Data written to the output port is read from the input port, with no intermediate buffering. Unlike some other kinds of ports, pipe ports do not need to be explicitly closed to be reclaimed by garbage collection.

If limit is #f, the new pipe holds an unlimited number of unread bytes (i.e., limited only by the available memory). If limit is a positive number, then the pipe will hold at most limit unread/unpeeked bytes; writing to the pipe’s output port thereafter will block until a read or peek from the input port makes more space available. (Peeks effectively extend the port’s capacity until the peeked bytes are read.)

The optional input-name and output-name are used as the names for the returned input and output ports, respectively.

> procedure (pipe-content-length pipe-port) → exact-nonnegative-integer?
> pipe-port : port?

Returns the number of bytes contained in a pipe, where pipe-port is either of the pipe’s ports produced by make-pipe. The pipe’s content length counts all bytes that have been written to the pipe and not yet read (though possibly peeked).
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