System.put_env

You're seeing just the function put_env, go back to System module for more information.

put_env(enum)

put_env(Enumerable.t()) :: :ok

Sets multiple environment variables.

Sets a new value for each environment variable corresponding to each {key, value} pair in enum.

put_env(binary(), binary()) :: :ok

Sets an environment variable value.

Sets a new value for the environment variable varname.