# Environment Variables

/// tip

If you already know what "environment variables" are and how to use them, feel free to skip this.

///

An environment variable (also known as "**env var**") is a variable that lives **outside** of the Python code, in the **operating system**, and could be read by your Python code (or by other programs as well).

<div class="termy">

```console
// Aqui ainda não definimos a variável de ambiente
$ python main.py

// Como não definimos a variável de ambiente, obtemos o valor padrão

Hello World from Python

// Mas se criarmos uma variável de ambiente primeiro
$ export MY_NAME="Wade Wilson"

// E então chamar o programa novamente
$ python main.py

// Agora ele pode ler a variável de ambiente

Hello Wade Wilson from Python
```

local g = import './g.libsonnet';
local var = g.dashboard.variable;

{
  datasource:
    var.datasource.new('datasource', 'prometheus'),

  cluster:
    var.query.new('cluster')
    + var.query.withDatasourceFromVariable(self.datasource)
    + var.query.queryTypes.withLabelValues(
      'cluster',
      'process_cpu_seconds_total',
    )
    + var.query.withRefresh('time')
    + var.query.selectionOptions.withMulti()

# Omgevingsvariabelen

/// tip

Als je al weet wat "omgevingsvariabelen" zijn en hoe je ze kunt gebruiken, kun je deze stap gerust overslaan.

///

Een omgevingsvariabele (ook bekend als "**env var**") is een variabele die **buiten** de Python-code leeft, in het **besturingssysteem** en die door je Python-code (of door andere programma's) kan worden gelezen.

		"Missing credential environment variable, \""+EnvRootUser+"\"",
		"Environment variable \""+EnvRootUser+"\" is missing",
		`Root user name (access key) and root password (secret key) are expected to be specified via environment variables MINIO_ROOT_USER and MINIO_ROOT_PASSWORD respectively`,
	)

	ErrMissingEnvCredentialRootPassword = newErrFn(
		"Missing credential environment variable, \""+EnvRootPassword+"\"",

# variables in it, OR may be left empty if the user has already exported the
# relevant variables in their environment. Because of 'set -o allexport' above
# (which is equivalent to "set -a"), every variable in the file is exported
# for other files to use.
#
# Separately, if TFCI is set *and* there are also additional TFCI_ variables

echo.
echo Please set the JAVA_HOME variable in your environment to match the
echo location of your Java installation.

goto fail

:findJavaFromJavaHome
set JAVA_HOME=%JAVA_HOME:"=%
set JAVA_EXE=%JAVA_HOME%/bin/java.exe

if exist "%JAVA_EXE%" goto execute

echo.
echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
echo.
echo Please set the JAVA_HOME variable in your environment to match the

    echo.
    echo Environment variables ^(read from context^):
    echo JAVA_OPTS          Environment variable, if unset uses ""
    echo SBT_OPTS           Environment variable, if unset uses ""
    echo ACTIVATOR_OPTS     Environment variable, if unset uses ""
    echo.

  # The string can then be piped into `source`, to re-set the
  # 'converted' variables.
  print(var_str)


if __name__ == '__main__':
  parser = argparse.ArgumentParser(description=(
      'Convert MSYS paths in environment variables to Windows paths.'))
  parser.add_argument('--blacklist',
                      nargs='*',
                      help='List of variables to ignore')
  parser.add_argument('--whitelist-prefix',

echo.
echo Please set the JAVA_HOME variable in your environment to match the
echo location of your Java installation.

goto fail

:findJavaFromJavaHome
set JAVA_HOME=%JAVA_HOME:"=%
set JAVA_EXE=%JAVA_HOME%/bin/java.exe

if exist "%JAVA_EXE%" goto execute

echo.
echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
echo.
echo Please set the JAVA_HOME variable in your environment to match the