# Processing (PDE) ant build Error

**URL:** <https://discourse.processing.org/t/processing-pde-ant-build-error/30890>\
**Category:** Processing\
**Created:** [June 24, 2021, 4:33pm UTC](https://discourse.processing.org/t/processing-pde-ant-build-error/30890 "2021-06-24T16:33:11Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Flolo](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.processing.org/flolo/32/13874_2.png) [@Flolo](https://discourse.processing.org/u/Flolo)\
**Post date:** [June 24, 2021, 4:33pm UTC](https://discourse.processing.org/t/processing-pde-ant-build-error/30890/1 "2021-06-24T16:33:11Z")

</div>

Hey I need some help.  
I want to change some code in the Processing (PDE).

That’s why I downloaded the [Github library](https://github.com/processing/processing).  
Then I copied the “app” folder to the desktop and opened it in eclipse. There were a few bugs as stated on the [website](https://github.com/processing/processing/wiki/Build-Instructions). so I followed the instructions:  
**You’ll have several errors, because you need to build the projects once with ant (on the command line: cd / path / to / processing / build && ant) so that the “generated” folder is created. After doing that, select the processing app project in Eclipse and hit F5 to refresh it.**

but every time I want to build it with ant (in the console), this error comes up:  
**C: \ Users \ chaos \ Desktop \ app \ build.xml: 13: Please build the core library first and make sure it is located at …/core/library/core.jar**

Does anyone have an idea of what I can do?