VT100: EXT + D              VT200: Find
    DEFINE_KEY Function: SPAWN

    Creates a subprocess under the current process. Use the
    LOGOUT command to terminate the subprocess. Because a tree of
    subprocesses can be established using the SPAWN function, you
    must be careful when terminating any process in the tree. When a
    process is terminated, all subprocesses below that point in the
    tree are terminated automatically.

    When you create a subprocess, you can specify an optional command
    string. The command string is executed within the created
    subprocess, and the subprocess terminates upon completion of
    the command.