# Standard streams - stdin - stdout - stderr

**URL:** <https://swi-prolog.discourse.group/t/standard-streams-stdin-stdout-stderr/4508>\
**Category:** Nice to know\
**Created:** [October 1, 2021, 8:02pm UTC](https://swi-prolog.discourse.group/t/standard-streams-stdin-stdout-stderr/4508 "2021-10-01T20:02:04Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![EricGT](https://avatars.discourse-cdn.com/v4/letter/e/f1d935/32.png) [@EricGT](https://swi-prolog.discourse.group/u/EricGT)\
**Post date:** [October 1, 2021, 8:02pm UTC](https://swi-prolog.discourse.group/t/standard-streams-stdin-stdout-stderr/4508/1 "2021-10-01T20:02:04Z")

</div>

Do you normally use a [standard stream](https://en.wikipedia.org/wiki/Standard_streams) expecting it work to only get an error like

```prolog
ERROR: with_output_to/2: stream `stdout' does not exist

```

Trying to find how SWI-Prolog defines them doesn’t always result in a hit.

Here is the documentation page you seek

[Predefined stream aliases](https://www.swi-prolog.org/pldoc/man?section=streamalias)