Input, Output, and Bidirectional Streams

ToC

Allegro CL

21 Streams

21.1 Stream Concepts

21.1.1 Introduction to Streams

21.1.1.1 Abstract Classifications of Streams

21.1.1.1.1 Input, Output, and Bidirectional Streams

A stream, whether a character stream or a binary stream, can be an input stream (source of data), an output stream (sink for data), both, or (e.g., when ":direction :probe" is given to open) neither.

The next figure shows operators relating to input streams.

Operators relating to Input Streams.
clear-input	read-byte	read-from-string
listen	read-char	read-line
peek-char	read-char-no-hang	read-preserving-whitespace
read	read-delimited-list	unread-char

The next figure shows operators relating to output streams.

Operators relating to Output Streams.
clear-output	prin1	write
finish-output	prin1-to-string	write-byte
force-output	princ	write-char
format	princ-to-string	write-line
fresh-line	print	write-string
pprint	terpri	write-to-string

A stream that is both an input stream and an output stream is called a bidirectional stream. See the functions input-stream-p and output-stream-p.

Any of the operators listed in Figure 21.1.1.1.1 Input, Output, and Bidirectional Streams or Figure 21.1.1.1.1 Input, Output, and Bidirectional Streams can be used with bidirectional streams. In addition, the next figure shows a list of operators that relate specificaly to bidirectional streams.

Operators relating to Bidirectional Streams.
y-or-n-p	yes-or-no-p