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get_stream(+StreamId, ?Stream)

Succeeds if Stream is the stream to which the stream StreamId is assigned.
+StreamId
Atom or integer.
?Stream
Integer, atom or variable.

Description

StreamId is an existing logical or physical stream. If Stream is a variable, then it is bound to the physical stream number corresponding to StreamId. Otherwise, the predicate succeeds if StreamId denotes the same stream as the symbolic stream name or physical stream number Stream.

The predefined logical system stream names are:

input, output, error, warning_output, log_output, stdin, stdout, stderr, null

Fail Conditions

Fails if Stream is not a stream with the stream identifier StreamId.

Resatisfiable

No.

Exceptions

(4) instantiation fault
One or both of StreamId and Stream is not instantiated.
(5) type error
Stream is neither an atom, an integer nor a variable.
(5) type error
StreamId is neither an atom nor an integer.
(193) illegal stream specification
StreamId is an illegal stream specification.

Examples

Success:
      [eclipse]: get_stream(input,X), set_stream(a,input),
      > get_stream(input,a).
      X = 0
      yes.

Fail:
      set_stream(b,4), get_stream(b, 10).

Error:
      get_stream(Id, S).      (Error 4).
      get_stream(1.0,S).      (Error 5).
      get_stream(3, S).       (Error 5).
      get_stream(blah,S).     (Error 193). % does not exist

See Also

set_stream / 2