Specify the build time environment variables

Environment variables are used to configure buildpack behavior. They may be specified by:

• The platform operator (this page)
• The end user (see Customize buildpack behavior with build-time environment variables)
• Other buildpacks (see Specify the environment)

When more than one entity specifies the same environment variable, the order of precedence is as shown above, with the platform operator having ultimate say over what the final value of the variable will be.

The platform operator specifies environment variables in a manner that is very similar to buildpacks (see XXX), but with a few differences. Namely:

• The directory for environment variable settings /cnb/build-config
• When no suffix is provided, the modification behavior is default For more information, consult the Platform Specification.

Example

Platform operators can make choices that “override” or provide defaults for application authors. In the following configuration the platform operator overrides the value of CGO_ENABLED for all application authors. The value of PIP_VERBOSE is set by default and can be overridden by buildpack authors or application authors. Any value for the environment variable CLASSPATH is prepended with the values provided by the platform operator.

$ tree /cnb/buildconfig/env
├── CGO_ENABLED.override
├── PIP_VERBOSE
└── CLASSPATH.prepend