# Environment variables on Julia 1.9

**URL:** <https://discourse.julialang.org/t/environment-variables-on-julia-1-9/87778>\
**Category:** New to Julia\
**Created:** [September 25, 2022, 11:33am UTC](https://discourse.julialang.org/t/environment-variables-on-julia-1-9/87778 "2022-09-25T11:33:02Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Brian1](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/brian1/32/49250_2.png) [@Brian1](https://discourse.julialang.org/u/Brian1)\
**Post date:** [September 25, 2022, 11:33am UTC](https://discourse.julialang.org/t/environment-variables-on-julia-1-9/87778/1 "2022-09-25T11:33:02Z")

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Julia 1.9.0-DEV has a new feature: `--heap-size-hint=<size>`. But how can I trigger it in Jupyter on Windows system? Like using mulitthreads, I could set the environment variable `JULIA_NUMS_THREADS` to 10. Is there a same way to do that with `--heap-size-hint=<size>`?  
I checked the documentation of Julia 1.9.0-DEV, [Environment Variables · The Julia Language](https://docs.julialang.org/en/v1.9-dev/manual/environment-variables/#Environment-Variables), while it is not mentioned.

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**Author:** ![Palli](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/palli/32/3380_2.png) [@Palli](https://discourse.julialang.org/u/Palli)\
**Post date:** [September 25, 2022, 11:44am UTC](https://discourse.julialang.org/t/environment-variables-on-julia-1-9/87778/2 "2022-09-25T11:44:22Z")

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I don’t think this is (yet) available with ENV. You could suggest it, but note 1.9 is in DEV, not out so this feature might go away (I doubt it though). I think it shouldn’t be needed, if the GC was actually better, more aggressive be default.

I don’t know if other languages have a similar option (then most likely Java, not Go I think). You could make a PR for an ENV, but while I think the option (as is) is is useful, at least as a debug option, I don’t think we’ll need this in the future, which is coming fast. There’s a lot going on with GC, many PRs already and some merged. People are doing good work on it.

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**Author:** ![Brian1](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/brian1/32/49250_2.png) [@Brian1](https://discourse.julialang.org/u/Brian1)\
**Post date:** [September 25, 2022, 12:48pm UTC](https://discourse.julialang.org/t/environment-variables-on-julia-1-9/87778/3 "2022-09-25T12:48:01Z")

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Yes, I tried, you are right. The default configuration usually has the best performace.

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**Author:** ![gbaraldi](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/gbaraldi/32/22101_2.png) [@gbaraldi](https://discourse.julialang.org/u/gbaraldi)\
**Post date:** [September 25, 2022, 12:57pm UTC](https://discourse.julialang.org/t/environment-variables-on-julia-1-9/87778/4 "2022-09-25T12:57:36Z")

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I can see some uses for it, but not for the normal user. But making an enviroment variable also an option is probably fine.

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**Author:** ![Elrod](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/elrod/32/22461_2.png) [@Elrod](https://discourse.julialang.org/u/Elrod)\
**Post date:** [September 25, 2022, 1:06pm UTC](https://discourse.julialang.org/t/environment-variables-on-julia-1-9/87778/5 "2022-09-25T13:06:55Z")

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> [@Brian1](#):
>
> But how can I trigger it in Jupyter on Windows system?

Install a kernel with the option. See [Installation · IJulia](https://julialang.github.io/IJulia.jl/stable/manual/installation/#Installing-additional-Julia-kernels)