Environment Variables

Note

You are free to use any combination of setting and accessing environment variables that you prefer. You must just ensure that the environment variables are set before you run the script that uses them, and that the environment variables are accessible from the script that uses them.

Python

---

defined using os.environ

In Python, you can define environment variables using the os.environ dictionary. The following code snippet demonstrates how to define an environment variable named VAR in Python:

import os

os.environ["VAR"] = "value"

Warning

This is not a recommended way to define environment variables for sensitive information such as API keys. This method is not secure, as the environment variables are stored in plain text in the Python script.

defined using python-dotenv

An alternative, more secure way to define environment variables in Python is to use the python-dotenv library. This library allows you to define environment variables in a .env file and load them into your Python script.

1. Install the python-dotenv library using pip:

   pip install python-dotenv
   

2. Create a .env file in the same directory as your Python script and define the environment variables in the following format:

   VAR=value
   

3. Load the environment variables into your Python script using the load_dotenv function:

   from dotenv import load_dotenv
   load_dotenv()
   

retrieved using os.environ.get

Following the definition of environment variables, you can access them in your Python script using the os.environ.get function.

import os

my_variable = os.environ.get("VAR",
                             None)  # Returns None if VAR is not set
if my_variable:
    # Use my_variable in your script
    print("VAR is set to:", my_variable)
else:
    # VAR is not set, handle the error appropriately
    print("VAR is not set.")

C++

---

defined using setenv

In C++, you can define environment variables using the setenv function.

#include <stdlib.h>

setenv("VAR", "value", 1);  // 1 indicates that the variable is overwritten if it already exists
                                    // 0 indicates that the variable is not overwritten if it already exists

retrieved using getenv

Following the definition of environment variables, you can access them in your C++ script using the getenv function.

#include <stdlib.h>

char* my_variable = getenv("VAR");

if (my_variable) {
    // Use my_variable in your script
    std::cout << "VAR is set to: " << my_variable << std::endl;
} else {
    // VAR is not set, handle the error appropriately
    std::cout << "VAR is not set." << std::endl;
}

Unix (Linux, macOS)

---

defined using export

In Unix-based systems, environment variables can be defined temporarily in the current terminal session using the export keyword. This can also be done within a Bash script (.sh).

export VAR="value"

defined in ~/.bashrc

In Unix-based systems, environment variables can be defined persistently across terminal sessions by adding the export statements to your shell profile file.

1. Open your shell profile file using a text editor ( e.g. nano ~/.bashrc).
2. Add the export statements to the file (preferably at the end).
3. Save the file and close the text editor.
4. Restart your terminal session.

5. Verify that the environment variables are set by running the following command:

   env | grep VAR
   

Note

If you are using zsh, you should use ~/.zshrc instead of ~/.bashrc.

retrieved using $VAR

Following the definition of environment variables, you can access them in your Bash script using the $VAR syntax.

if [ -n "$VAR" ]; then
    # Use $VAR in your script
    echo "VAR is set to: $VAR"
else
    # VAR is not set, handle the error appropriately
    echo "VAR is not set."
fi

Windows

---

defined using set

In Windows, environment variables can be defined temporarily in the current terminal session using the set keyword. This can also be done within a Batch script (.bat).

set VAR=value

defined using setx

In Windows, environment variables can be defined persistently across terminal sessions by adding the setx statements to your system environment variables.

1. Open the "System Properties" window by pressing Windows + Pause/Break on your keyboard.
2. Click "Advanced system settings" on the left.
3. Click "Environment Variables" on the bottom right.
4. Click "New" under "System variables" and add the environment variables.
5. Click "OK" to save the changes.
6. Restart your terminal session.

7. Verify that the environment variables are set by running the following command:

   set | findstr VAR
   

retrieved using %VAR%

Following the definition of environment variables, you can access them in your Batch script using the %VAR% syntax.

if defined VAR (
    rem Use %VAR% in your script
    echo VAR is set to: %VAR%
) else (
    rem VAR is not set, handle the error appropriately
    echo VAR is not set.
)

Azure Pipelines

---

Note

This section is intended for maintainers of the feedstock repositories (at current). If you are not a maintainer, you can safely ignore this section.

1. Navigate to dev.azure.com and sign in.

1. Click the feedstock-builds project under the tudat-team organization.

defined for a pipeline

1. After navigating to the project, click " Pipelines" under the feedstock-builds project.

1. Click on the specific pipeline in which you want to set the environment variable (e.g. tudat-feedstock).

1. Click "Edit" in the top-right of the page.

1. Click "Variables" in the top-right of the page.

1. Update an existing token (e.g. BINSTAR_TOKEN), or create a new one with the + icon.

!!! note It is crucial to keep the environment variables private and secure. Ensure that you do not share them or commit them to a public repository, as this could lead to security issues.

defined across all pipelines

Failure

This section is the desired way of defining environment variables in Azure. However, it is currently not possible to define environment variables in an Azure project due to conda-smithy overwriting the pipeline.yaml. This is a known issue, and we are working on a solution. In the meantime, please use the method described in the previous section. This section therefore exists for future reference.

1. After navigating to the project, click " Library" under the feedstock-builds project and select the target " variable group".

1. Add a new variable by clicking + Add or edit an existing one by clicking the name of value of the variable.

1. Make the variable group available by adding the following lines to the pipeline.yaml file in the root of the feedstock repository.

   variables:
     - group: <variable_group_name>
   

!!! note The <variable_group_name> should be the name of the variable group you created in step 1.

!!! failure As mentioned, this will be overwritten by conda-smithy. It was expected that by adding:

    ```yaml
    azure:
       variables:
         - group: <variable_group_name>
    ```

    to the `conda-forge.yml` file, the `pipeline.yaml` would be updated accordingly, as [hinted at here](https://conda-forge.org/docs/maintainer/conda_forge_yml.html#azure). However, this is not the case. We are working on a solution.