Return type: Switch
Returns:        true if the stream is attached to a destination and false otherwise. Replacing is with isnt will reverse the result.

Syntax

stream-name (is | isnt) attached 

or

#current-output (is | isnt) attached 

or 

#current-input (is | isnt) attached 
    

is attached is a a stream test used to determine whether a stream is attached to a destination.

Usage Notes

A stream can have three states:

• unattached, the initial state,
• opened, or
• closed.

When a stream is attached, its destination can be any one of five types:

• a buffer,
• a file,
• a referent,
• an external string sink function, or
• #markup-parser.

The is attached test can also be applied to #current-input, to determine when #current-input can supply data to a string sink or markup sink.

Related Syntax close discard open reopen set is closed is open

Related Concepts Streams: attachments

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