Contents

• Overview
• Example usage: Use an environment variable
• Example usage: Set an environment variable
• Similar recipes
• Regression test: Values containing variable substitution syntax breaks things

Overview

This recipe allows to set and get environment variables during the execution of a buildout.

The recipe mirrors the current environment variables into its section, so that e.g. ${environment:USER} will give the current user.

To set an environment variable you just set it in the section.

The environment variables are set and get during the initialization of the Recipe instance, i.e. after buildout.cfg is read but before any recipe is installed or updated.

Example usage: Use an environment variable

We'll start by creating a buildout that uses the recipe:

>>> write('buildout.cfg',
... """
... [buildout]
... parts = environment print
...
... [some-section]
... some-option = ${environment:SOME_VARIABLE}
...
... [environment]
... recipe = collective.recipe.environment
...
... [print]
... recipe = mr.scripty
... install =
...     ... print(self.buildout['some-section']['some-option'])
...     ... return []
... """)

The mr.scripty recipe is used to print out the value of the ${some-section:some-option} option.

Now we set the environment variable:

>>> import os
>>> os.environ['SOME_VARIABLE'] = 'some_value'

Running the buildout gives us:

>>> run_buildout()
START...
some_value
...END

Example usage: Set an environment variable

We'll start by creating a buildout that uses the recipe:

>>> write('buildout.cfg',
... """
... [buildout]
... parts = environment print
...
... [some-section]
... some-option = value2
...
... [environment]
... recipe = collective.recipe.environment
... var1 = value1
... var2 = ${some-section:some-option}
...
... [print]
... recipe = mr.scripty
... install =
...     ... import os
...     ... for var in ('var1', 'var2'):
...     ...     print('%s = %s' % (var, os.environ[var]))
...     ... return []
... """)

The mr.scripty recipe is used to print out the values of the environment variables.

Running the buildout gives us:

>>> run_buildout()
START...
var1 = value1
var2 = value2
...END

Similar recipes

The functionality to mirror the environment variables into the recipe's section is largely copied from gocept.recipe.env.

Regression test: Values containing variable substitution syntax breaks things

Problem: if an environment variable value contains something looking like variable substitution in Buildout syntax then things break. We fix this by escaping the variable substitutions using two dollar signs. Eg.: ${foo} becomes $${foo}.

Let's see if it works.

Set environment variables:

>>> os.environ['PROBLEM_VAR_1'] = '${foo}'
>>> os.environ['PROBLEM_VAR_2'] = '${foo:bar}'
>>> os.environ['PROBLEM_VAR_3'] = 'Contains ${foo} and also ${foo:bar}.'
>>> os.environ['LEGAL_VAR_1'] = '$foo'
>>> os.environ['LEGAL_VAR_2'] = '{foo}'

Write a buildout using those variables:

>>> write('buildout.cfg',
... """
... [buildout]
... parts = environment print
...
... [some-section]
... option-1 = ${environment:PROBLEM_VAR_1}
... option-2 = ${environment:PROBLEM_VAR_2}
... option-3 = ${environment:PROBLEM_VAR_3}
... option-4 = ${environment:LEGAL_VAR_1}
... option-5 = ${environment:LEGAL_VAR_2}
...
... [environment]
... recipe = collective.recipe.environment
...
... [print]
... recipe = mr.scripty
... install =
...     ... section = self.buildout['some-section']
...     ... for (k, v) in sorted(section.items()):
...     ...     print('{} = {}'.format(k, v))
...     ... return []
...
... """)

Running the buildout gives us:

>>> run_buildout()
START...
option-1 = $${foo}
option-2 = $${foo:bar}
option-3 = Contains $${foo} and also $${foo:bar}.
option-4 = $foo
option-5 = {foo}
...END