# Sleep/1 on Linux

**URL:** <https://swi-prolog.discourse.group/t/sleep-1-on-linux/9352>\
**Category:** Help!\
**Created:** [October 18, 2025, 10:54am UTC](https://swi-prolog.discourse.group/t/sleep-1-on-linux/9352 "2025-10-18T10:54:55Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![aldragon-git](https://yyz2.discourse-cdn.com/free1/user_avatar/swi-prolog.discourse.group/aldragon-git/32/6865_2.png) [@aldragon-git](https://swi-prolog.discourse.group/u/aldragon-git)\
**Post date:** [October 18, 2025, 10:54am UTC](https://swi-prolog.discourse.group/t/sleep-1-on-linux/9352/1 "2025-10-18T10:54:55Z")

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I’m using: SWI-Prolog version 9.2.9

sleep/1 does not run anymore

```prolog
?- sleep(10).
false.

```

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**Author:** ![jan](https://yyz2.discourse-cdn.com/free1/user_avatar/swi-prolog.discourse.group/jan/32/4_2.png) [@jan](https://swi-prolog.discourse.group/u/jan)\
**Post date:** [October 18, 2025, 11:24am UTC](https://swi-prolog.discourse.group/t/sleep-1-on-linux/9352/2 "2025-10-18T11:24:05Z")

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Without details there is not much to say. Did it ever work? How did you install this version? Is any other code loaded that may be redefining sleep/1? The last seems the most plausible. Try

```
?- predicate_property(sleep(_), Prop).

```

That should give `built_in`, `foreign` and `imported_from(system)` (and a couple of others).

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<div class="post-metadata">

**Author:** ![aldragon-git](https://yyz2.discourse-cdn.com/free1/user_avatar/swi-prolog.discourse.group/aldragon-git/32/6865_2.png) [@aldragon-git](https://swi-prolog.discourse.group/u/aldragon-git)\
**Post date:** [October 18, 2025, 12:28pm UTC](https://swi-prolog.discourse.group/t/sleep-1-on-linux/9352/3 "2025-10-18T12:28:10Z")

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THANKS Jan  
this is the answer  
?- predicate\_property(sleep(\_), Prop).  
Prop = interpreted ;  
Prop = visible ;  
Prop = static ;  
Prop = file(‘/home/aldo/IA/AA2025-26/ricercaSpazioStati/dimostratore.pl’) ;  
Prop = line\_count(94) ;  
Prop = number\_of\_clauses(1) ;  
Prop = number\_of\_rules(0) ;  
Prop = last\_modified\_generation(17296) ;  
Prop = defined ;  
Prop = size(248).

I’ve just re-installed the binary through  
sudo apt-get -y install swi-prolog-full

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<div class="post-metadata">

**Author:** ![aldragon-git](https://yyz2.discourse-cdn.com/free1/user_avatar/swi-prolog.discourse.group/aldragon-git/32/6865_2.png) [@aldragon-git](https://swi-prolog.discourse.group/u/aldragon-git)\
**Post date:** [October 18, 2025, 12:34pm UTC](https://swi-prolog.discourse.group/t/sleep-1-on-linux/9352/4 "2025-10-18T12:34:26Z")

</div>

sounds strange …  
now it seems to work again …  
sorry, let me think a bit for that …  
sorry

[SOLVED]  
in the consulted file there was a period (.) instead of a comma (,) before the call to sleep(\_), so the predicate was beed REDEFINED …

Sorry for having bothered you  
Bye and THANKS SO MUCH …