Search path environments
The search path is a chain of environments containing exported functions of attached packages.
The API includes:
base::search() to get the names of environments attached to the
search path.
search_envs() returns the environments on the search path as a
list.
pkg_env_name() takes a bare package name and prefixes it with
"package:". Attached package environments have search names of
the form package:name.
pkg_env() takes a bare package name and returns the scoped
environment of packages if they are attached to the search path,
and throws an error otherwise. It is a shortcut for
search_env(pkg_env_name("pkgname")).
global_env() and base_env() (simple aliases for globalenv()
and baseenv()). These are respectively the first and last
environments of the search path.
is_attached() returns TRUE when its argument (a search name
or a package environment) is attached to the search path.
search_envs() search_env(name) pkg_env(pkg) pkg_env_name(pkg) is_attached(x) base_env() global_env()
name |
The name of an environment attached to the search
path. Call |
pkg |
The name of a package. |
x |
An environment or a search name. |
This chain of environments determines what objects are visible from the global workspace. It contains the following elements:
The chain always starts with global_env() and finishes with
base_env() which inherits from the terminal environment
empty_env().
Each base::library() call attaches a new package environment to
the search path. Attached packages are associated with a search name.
In addition, any list, data frame, or environment can be attached
to the search path with base::attach().
# List the search names of environments attached to the search path:
search()
# Get the corresponding environments:
search_envs()
# The global environment and the base package are always first and
# last in the chain, respectively:
envs <- search_envs()
envs[[1]]
envs[[length(envs)]]
# These two environments have their own shortcuts:
global_env()
base_env()
# Packages appear in the search path with a special name. Use
# pkg_env_name() to create that name:
pkg_env_name("rlang")
search_env(pkg_env_name("rlang"))
# Alternatively, get the scoped environment of a package with
# pkg_env():
pkg_env("utils")Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.