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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.

Calling Modes

get_stream(+, -)
get_stream(+, +)

Description

StreamId is an existing symbolic or physical stream identifier. If Stream is a variable, it will get bound to the physical stream number corresponding to StreamId. If Stream is an existing symbolic or physical stream identifier, then the predicate succeeds iff StreamId and Stream denote the same physical stream.

The predefined symbolic 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).
      X = 0
      yes.

      [eclipse]: set_stream(a,input), get_stream(input,a), get_stream(a,input).
      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