# How to wait until all files are processed at a task for next step?

**URL:** <https://community.seqera.io/t/how-to-wait-until-all-files-are-processed-at-a-task-for-next-step/472>\
**Category:** Ask for help\
**Created:** [February 10, 2024, 4:26pm UTC](https://community.seqera.io/t/how-to-wait-until-all-files-are-processed-at-a-task-for-next-step/472 "2024-02-10T16:26:05Z")\
**Posts on this page:** 1\
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**Author:** ![mribeirodantas](https://dub1.discourse-cdn.com/flex013/user_avatar/community.seqera.io/mribeirodantas/32/235_2.png) [@mribeirodantas](https://community.seqera.io/u/mribeirodantas)\
**Post date:** [February 12, 2024, 12:11am UTC](https://community.seqera.io/t/how-to-wait-until-all-files-are-processed-at-a-task-for-next-step/472/5 "2024-02-12T00:11:47Z")

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> [@complexgenome](#):
>
> Missing process or function collect([DataflowStream[?], DataflowStream[?]])

I believe the cause of this is that your process has a multi-channel output and `collect` doesn’t know what to do with it. That’s what the error message is saying. You should apply the `collect` channel operator to each channel and pass it to the next process.

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