[ Stream I/O | The ECLiPSe Built-In Predicates | Reference Manual | Alphabetic Index ]

# 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 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

### Modes and Determinism

- get_stream(+, -) is det
- get_stream(+, +) is semidet

### Fail Conditions

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

### 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

## See Also

set_stream / 2