6 The Standard-IO Module

6.2 Handling standard input and output

The Standard-IO module provides a Dylan interface to the standard I/O facility of operating systems such as MS-DOS or UNIX.

The module consists of three variables, each of which is bound to a stream.

*standard-input*

Variable

: An input stream that reads data from the platform's standard input location. It is equivalent to the Java stream java.lang.System.in.

*standard-output*

Variable

: An output stream that sends data to the platform's standard output location. It is equivalent to the Java stream java.lang.System.out.

*standard-error*

Variable

: An output stream that sends data to the platform's standard error location. It is equivalent to the Java stream java.lang.System.err.

For console-based applications (i.e., applications that run in character mode), the three streams just use the console window in which the application was started.

For purely window-based applications, each variable is bound by default to a stream that lazily creates a console window as soon as any input is requested or output is performed. Only one window is created, and this is shared between all three streams. Any subsequent input or output uses the same window. The window that is created uses the standard configuration settings set by the user. For example, the window is only scrollable if all console windows are configured to be scrollable on the machine running the application.

For more information about streams, please refer to Chapter 5, "The Streams Module".