Environment

Warning

This is a very experimental feature and it will have breaking changes in future releases.

Environment is a generic class that helps defining modifications to the environment variables. This class is used by other tools like the conan.tools.gnu autotools helpers and the VirtualBuildEnv and VirtualRunEnv generator. It is important to highlight that this is a generic class, to be able to use it, a specialization for the current context (shell script, bat file, path separators, etc), a EnvVars object needs to be obtained from it.

Variable declaration

from conan.tools.env import Environment

def generate(self):
    env = Environment()
    env.define("MYVAR1", "MyValue1")  # Overwrite previously existing MYVAR1 with new value
    env.append("MYVAR2", "MyValue2")  # Append to existing MYVAR2 the new value
    env.prepend("MYVAR3", "MyValue3") # Prepend to existing MYVAR3 the new value
    env.remove("MYVAR3", "MyValue3")  # Remove the MyValue3 from MYVAR3
    env.unset("MYVAR4")               # Remove MYVAR4 definition from environment

    # And the equivalent with paths
    env.define_path("MYPATH1", "path/one")  # Overwrite previously existing MYPATH1 with new value
    env.append_path("MYPATH2", "path/two")  # Append to existing MYPATH2 the new value
    env.prepend_path("MYPATH3", "path/three") # Prepend to existing MYPATH3 the new value

The “normal” variables (the ones declared with define, append and prepend) will be appended with a space, by default, but the separator argument can be provided to define a custom one.

The “path” variables (the ones declared with define_path, append_path and prepend_path) will be appended with the default system path separator, either : or ;, but it also allows defining which one.

Composition

Environments can be composed:

from conan.tools.env import Environment

env1 = Environment()
env1.define(...)
env2 = Environment()
env2.append(...)

env1.compose_env(env2) # env1 has priority, and its modifications will prevail

Obtaining environment variables

You can obtain an EnvVars object with the vars() method like this:

from conan.tools.env import Environment

def generate(self):
    env = Environment()
    env.define("MYVAR1", "MyValue1")
    envvars = env.vars(self, scope="build")
    # use the envvars object

The default scope is equal "build", which means that if this envvars generate a script to activate the variables, such script will be automatically added to the conanbuild.sh|bat one, for users and recipes convenience. Conan generators use build and run scope, but it might be possible to manage other scopes too.

Environment definition

There are some other places where Environment can be defined and used:

In recipes package_info() method, in new self.buildenv_info and self.runenv_info, this environment will be propagated via VirtualBuildEnv and VirtualRunEnv respectively to packages depending on this recipe.
In generators like AutootoolsDeps, AutotoolsToolchain, that need to define environment for the current recipe.
In profiles new [buildenv] section.

The definition in package_info() is as follow, taking into account that both self.buildenv_info and self.runenv_info are objects of Environment() class.

from conans import ConanFile

class App(ConanFile):
    name = "mypkg"
    version = "1.0"
    settings = "os", "arch", "compiler", "build_type"

    def package_info(self):
        # This is information needed by consumers to build using this package
        self.buildenv_info.append("MYVAR", "MyValue")
        self.buildenv_info.prepend_path("MYPATH", "some/path/folder")

        # This is information needed by consumers to run apps that depends on this package
        # at runtime
        self.runenv_info.define("MYPKG_DATA_DIR", os.path.join(self.package_folder,
                                                               "datadir"))