Switches control of your terminal from your current process to
    another process.

    The ATTACH command allows you to move between processes that you
    create with the SPAWN command. For example, while you are editing
    a file, use the SPAWN command to move to a subprocess (Mail) to
    read a new mail message. Then enter ATTACH to move back to the
    editing session. If you want to read another new mail message,
    enter the ATTACH command to move back to the Mail subprocess you
    already created.

    Format

      ATTACH  [process-name]