# Dealing with long list of environmental variables **URL:** \ **Category:** Cylc Support\ **Created:** [August 1, 2024, 2:01pm UTC](https://cylc.discourse.group/t/dealing-with-long-list-of-environmental-variables/993 "2024-08-01T14:01:44Z")\ **Posts on this page:** 1\ **Showing post:** 4
**Author:** ![oliver.sanders](https://yyz2.discourse-cdn.com/free1/user_avatar/cylc.discourse.group/oliver.sanders/32/110_2.png) [@oliver.sanders](https://cylc.discourse.group/u/oliver.sanders)\ **Post date:** [August 1, 2024, 4:46pm UTC](https://cylc.discourse.group/t/dealing-with-long-list-of-environmental-variables/993/4 "2024-08-01T16:46:56Z")
Thanks for that information. > The shell script then creates on the fly other scripts that are submitted to slurm. 🤮 The fun of workflows implemented in shell scripts! The most amusing ones submit themselves to the queue in an endless chain of submissions. ### Cylc Task Environment Variables In Cylc you can define environment variables like this: ```ini # flow.cylc [runtime] [[mytask]] script = my-script # these env-vars will be avilable to "my-script" when it runs [[[environment]]] ENV_VAR_1 = value-1 ENV_VAR_2 = value-2 ENV_VAR_3 = value-3 # and so on ``` You can set environment variables for groups of tasks, or for all tasks by using the appropriate “family” helping to cut down on duplication, e.g: ```ini # flow.cylc [runtime] [[root]] # these env vars will be available to all tasks: [[[environment]]] ENV_VAR_1 = value-1 ENV_VAR_2 = value-2 ENV_VAR_3 = value-3 # and so on [[mytask1]] script = my-script-1 [[mytask2]] script = my-script-2 ``` When workflow configuration files get large, they can be broken down into smaller parts using [include files](https://cylc.github.io/cylc-doc/stable/html/workflow-design-guide/general-principles.html#include-files) e.g: ```ini # flow.cylc %include environment.cylc [runtime] [[mytask]] script = my-script ``` ```auto # environment.cylc [runtime] [[root]] # these env vars will be available to all tasks: [[[environment]]] ENV_VAR_1 = value-1 ENV_VAR_2 = value-2 ENV_VAR_3 = value-3 # and so on ``` You can continue with using a script to define environment variables if desired: ```ini [runtime] [[mytask]] env-script = source environment.sh script = my-script ``` ### Rose Applications Configuring environment variables like this works fine for simple tasks, but as the complexity of the problem grows, you might end up with large numbers of environment variables, as well as other “resources” such as: - Namelists (fortran). - Static files. - External resources (e.g. in Git / SVN repos). - CLI arguments. - etc. At this point, you might consider bundling all this up into an “application”. Rose is a tool which can do all that enabling you to bundle up those dangling resources and variables into a single isolated unit. A simple Rose application might look like this: ```auto # apps/mytask/rose-app.conf [command] default=my-script [env] ENV_VAR_1 = value-1 ENV_VAR_2 = value-2 ENV_VAR_3 = value-3 ``` It can be run by itself like so: ```shell $ rose app-run -C /path/to/app ``` Or run by a Cylc task like so: ```ini [runtime] [[mytask]] # this will look for an app in "apps/mytask" script = rose task-run ``` Everything in a Rose application can be assigned metadata as desired, e.g. a title & description. Environment variables can be assigned a type as well as rules which govern what values the variable can be set to. Rose applications are “configurations”, Rose provides a GUI called `rose edit` which makes use of this metadata and can be used to edit these configurations. Note, the `rose edit` GUI is currently only available in the legacy Rose 2019 release, but is not required. Porting work for the GUI will begin soon. So, using a Rose application allows you to pull environment variables (and other things) out of the `flow.cylc` file and into a dedicated file for that particular task. Rose is entirely optional, but has good integration with Cylc. Cylc workflows which use Rose applications will often also provide a `rose-suite.conf` file to configure the workflow itself, again entirely optional. For more information, this [Rose tutorial](https://metomi.github.io/rose/doc/html/tutorial/rose/applications.html) takes you through the process of turning an over-complex Cylc task into a Rose application. ### Installing Rose Via conda/mamba: `conda install cylc-flow=8.3 cylc-rose` Via pip: `pip install cylc-flow=='8.3.*' cylc-rose` If you are interested in installing the legacy `rose edit` GUI, the installation instructions are [here](https://metomi.github.io/rose/2019.01.8/html/installation.html), it is possible to use this in combination with the newer version of Rose by using a [wrapper script](https://cylc.github.io/cylc-doc/stable/html/installation.html#managing-environments) to manage the environments (can provide further details if desired). --- _[View the full topic](https://cylc.discourse.group/t/dealing-with-long-list-of-environmental-variables/993)._