-- environment
os.environ
os.setenv(name, value, overwrite)
os.unsetenv(name)

-- miscellaneous
os.sleep(seconds)

-- file system
os.dir
file = os.file

-- process control
pid = os.spawn(filename, {args={}, env={}, stdin=io_file, stdout=io_file, stderr=io_file})
exitcode = os.wait(pid)