def _is_prefixed(cmd_line):
    """Whether the supplied command line has already been prefixed
    with an OS specific operation.
    """
    if cmd_line is None:
        raise ValueError("CommandLine is required field for task.")
    return cmd_line.startswith('cmd.exe /c') or \
        cmd_line.startswith('cmd /c') or \
        cmd_line.startswith('/bin/bash -c') or \
        cmd_line.startswith('/bin/sh -c')