# Environment variables (/docs/sandbox/environment-variables)

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Related: [Auto-resume on request](/docs/sandbox/auto-resume.md), [Connect to running sandbox](/docs/sandbox/connect.md), [Filesystem-only snapshots](/docs/sandbox/filesystem-only-snapshots.md), [Sandbox forking](/docs/sandbox/fork.md), [Git integration](/docs/sandbox/git-integration.md), [Monitor sandbox lifecycle events](/docs/sandbox/lifecycle-events-api.md)

This page covers how to set and use environment variables in a sandbox, and default environment variables inside the sandbox.

## Default environment variables [#default-environment-variables]

### Knowing if you are inside a sandbox [#knowing-if-you-are-inside-a-sandbox]

Sometimes it's useful to know if the code is running inside a sandbox. Upon creating a sandbox, useful sandbox metadata is set as environment variables for commands:

* `E2B_SANDBOX` is set to `true` for processes to know if they are inside our VM.
* `E2B_SANDBOX_ID` to know the ID of the sandbox.
* `E2B_TEMPLATE_ID` to know what template was used for the current sandbox.

You can try it out by running the following code in the sandbox:

<CodeGroup>
  <CodeBlockTabs defaultValue="JavaScript & TypeScript" groupId="javascript-typescript+python">
    <CodeBlockTabsList>
      <CodeBlockTabsTrigger value="JavaScript & TypeScript">
        JavaScript & TypeScript
      </CodeBlockTabsTrigger>

      <CodeBlockTabsTrigger value="Python">
        Python
      </CodeBlockTabsTrigger>
    </CodeBlockTabsList>

    <CodeBlockTab value="JavaScript & TypeScript">
      ```js  
      const sandbox = await Sandbox.create()
      const result = await sandbox.commands.run('echo $E2B_SANDBOX_ID')
      ```
    </CodeBlockTab>

    <CodeBlockTab value="Python">
      ```python  
      sandbox = Sandbox.create()
      result = sandbox.commands.run("echo $E2B_SANDBOX_ID")
      ```
    </CodeBlockTab>
  </CodeBlockTabs>
</CodeGroup>

<Note>
  These default environment variables are only accessible via the SDK, when using the CLI you can find them in the form of dot files in the `/run/e2b/` dir:

  ```sh
  user@e2b:~$ ls -a /run/e2b/
  .E2B_SANDBOX  .E2B_SANDBOX_ID  .E2B_TEMPLATE_ID
  ```
</Note>

***

## Setting environment variables [#setting-environment-variables]

There are 3 ways to set environment variables in a sandbox:

1. [Global environment variables when creating the sandbox](/docs/sandbox/environment-variables#1-global-environment-variables).
2. [When running code in the sandbox](/docs/sandbox/environment-variables#2-setting-environment-variables-when-running-code).
3. [When running commands in the sandbox](/docs/sandbox/environment-variables#3-setting-environment-variables-when-running-commands).

### 1. Global environment variables [#1-global-environment-variables]

You can set global environment variables when creating a sandbox.

<CodeGroup>
  <CodeBlockTabs defaultValue="JavaScript & TypeScript" groupId="javascript-typescript+python">
    <CodeBlockTabsList>
      <CodeBlockTabsTrigger value="JavaScript & TypeScript">
        JavaScript & TypeScript
      </CodeBlockTabsTrigger>

      <CodeBlockTabsTrigger value="Python">
        Python
      </CodeBlockTabsTrigger>
    </CodeBlockTabsList>

    <CodeBlockTab value="JavaScript & TypeScript">
      ```js highlight={2-4}  
      const sandbox = await Sandbox.create({
        envs: {
          MY_VAR: 'my_value',
        },
      })
      ```
    </CodeBlockTab>

    <CodeBlockTab value="Python">
      ```python highlight={2-4}  
      sandbox = Sandbox.create(
        envs={
          'MY_VAR': 'my_value',
        },
      )
      ```
    </CodeBlockTab>
  </CodeBlockTabs>
</CodeGroup>

### 2. Setting environment variables when running code [#2-setting-environment-variables-when-running-code]

You can set environment variables for specific code execution call in the sandbox.

<Note>
  * These environment variables are scoped to the command but are not private in the OS.
  * If you had a global environment variable with the same name, it will be overridden only for the command.
</Note>

<CodeGroup>
  <CodeBlockTabs defaultValue="JavaScript & TypeScript" groupId="javascript-typescript+python">
    <CodeBlockTabsList>
      <CodeBlockTabsTrigger value="JavaScript & TypeScript">
        JavaScript & TypeScript
      </CodeBlockTabsTrigger>

      <CodeBlockTabsTrigger value="Python">
        Python
      </CodeBlockTabsTrigger>
    </CodeBlockTabsList>

    <CodeBlockTab value="JavaScript & TypeScript">
      ```js highlight={3-5}  
      const sandbox = await Sandbox.create()
      const result = await sandbox.runCode('import os; print(os.environ.get("MY_VAR"))', {
        envs: {
          MY_VAR: 'my_value',
        },
      })
      ```
    </CodeBlockTab>

    <CodeBlockTab value="Python">
      ```python highlight={4-6}  
      sandbox = Sandbox.create()
      result = sandbox.run_code(
          'import os; print(os.environ.get("MY_VAR"))',
          envs={
              'MY_VAR': 'my_value'
          }
      )
      ```
    </CodeBlockTab>
  </CodeBlockTabs>
</CodeGroup>

### 3. Setting environment variables when running commands [#3-setting-environment-variables-when-running-commands]

You can set environment variables for specific command execution in the sandbox.

<Note>
  * These environment variables are scoped to the command but are not private in the OS.
  * If you had a global environment variable with the same name, it will be overridden only for the command.
</Note>

<CodeGroup>
  <CodeBlockTabs defaultValue="JavaScript & TypeScript" groupId="javascript-typescript+python">
    <CodeBlockTabsList>
      <CodeBlockTabsTrigger value="JavaScript & TypeScript">
        JavaScript & TypeScript
      </CodeBlockTabsTrigger>

      <CodeBlockTabsTrigger value="Python">
        Python
      </CodeBlockTabsTrigger>
    </CodeBlockTabsList>

    <CodeBlockTab value="JavaScript & TypeScript">
      ```js highlight={3-5}  
      const sandbox = await Sandbox.create()
      sandbox.commands.run('echo $MY_VAR', {
        envs: {
          MY_VAR: '123',
        },
      })
      ```
    </CodeBlockTab>

    <CodeBlockTab value="Python">
      ```python highlight={4-6}  
      sandbox = Sandbox.create()
      sandbox.commands.run(
          'echo $MY_VAR',
          envs={
              'MY_VAR': '123'
          }
      )
      ```
    </CodeBlockTab>
  </CodeBlockTabs>
</CodeGroup>