Chdir changes the current working directory to the named directory.

Getenv retrieves the value of the environment variable named by the key.

Getwd returns a rooted path name corresponding to the current directory.

LoadModule loads the os module.

Mkdir creates a new directory with the specified name and permission bits (before umask).

MkdirAll creates a directory named path, along with any necessary parents.

ReadFile reads the file named by filename and returns the contents.

Remove removes the named file or (empty) directory.

RemoveAll removes path and any children it contains.

Rename renames (moves) oldpath to newpath.

Setenv sets the value of the environment variable named by the key.

WriteFile writes data to a file named by filename.

ModuleName defines the expected name for this Module when used in starlark's load() function, eg: load('io/ioutil', 'json').