# Writeln('abc') fails, after consult - Prolog (threaded, 64 bits, version 8.3.21)

**URL:** <https://swi-prolog.discourse.group/t/writeln-abc-fails-after-consult-prolog-threaded-64-bits-version-8-3-21/3872>\
**Category:** Help!\
**Created:** [April 26, 2021, 8:57am UTC](https://swi-prolog.discourse.group/t/writeln-abc-fails-after-consult-prolog-threaded-64-bits-version-8-3-21/3872 "2021-04-26T08:57:18Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![grossdan](https://yyz2.discourse-cdn.com/free1/user_avatar/swi-prolog.discourse.group/grossdan/32/23_2.png) [@grossdan](https://swi-prolog.discourse.group/u/grossdan)\
**Post date:** [April 26, 2021, 8:57am UTC](https://swi-prolog.discourse.group/t/writeln-abc-fails-after-consult-prolog-threaded-64-bits-version-8-3-21/3872/1 "2021-04-26T08:57:18Z")

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Hello,

After consulting my code, I suddenly have an odd error, a call to writeln/1 fails in my code and on the command line.

Before consulting writeln/1 works fine.

I tried to see if i somehow redefined writeln – although, i don’t recall having done that – and indeed i can’t find any redefined code – also when trying to retrieve writeln via clause/2 – clause fails.

Is this a known issue?

Right now, my work around is to exchange writelns with format or perhaps print …

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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:** [April 26, 2021, 9:35am UTC](https://swi-prolog.discourse.group/t/writeln-abc-fails-after-consult-prolog-threaded-64-bits-version-8-3-21/3872/2 "2021-04-26T09:35:02Z")

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> [@grossdan](#):
>
> also when trying to retrieve writeln via [clause/2](https://www.swi-prolog.org/pldoc/doc_for?object=clause/2) – clause fails.

clause/2 on writeln/1 is supposed to generate a permission error. It failing probably means you defined it. Possibly as dynamic or multifile? Try check/0 or predicate\_property/2. Of course, a `git grep -w writeln` can help as well 🙂

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**Author:** ![grossdan](https://yyz2.discourse-cdn.com/free1/user_avatar/swi-prolog.discourse.group/grossdan/32/23_2.png) [@grossdan](https://swi-prolog.discourse.group/u/grossdan)\
**Post date:** [April 26, 2021, 9:36am UTC](https://swi-prolog.discourse.group/t/writeln-abc-fails-after-consult-prolog-threaded-64-bits-version-8-3-21/3872/3 "2021-04-26T09:36:06Z")

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> [@jan](#):
>
> `grep -w writeln` can help as well

yea, i tried that – requires eye-balling (unfortunately) many entries – will do it again – until i find the culpit 🙂

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**Author:** ![grossdan](https://yyz2.discourse-cdn.com/free1/user_avatar/swi-prolog.discourse.group/grossdan/32/23_2.png) [@grossdan](https://swi-prolog.discourse.group/u/grossdan)\
**Post date:** [April 26, 2021, 9:37am UTC](https://swi-prolog.discourse.group/t/writeln-abc-fails-after-consult-prolog-threaded-64-bits-version-8-3-21/3872/4 "2021-04-26T09:37:59Z")

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ahh - i found it – its a comma turned dot, in the body of a clause – causing a standalone writeln 🙂