def _get_body(script_lines, num_cores_simul, silence=False):
    """Function to create the body of the script files, staging their start.

    Arguments
    ---------
    script_lines: str
        List of strings where each element is one command to be submitted.
    sum_cores_simul: int
        Number of cores used simultaneously.
    Returns
    -------
    str:
        Joined commands.
    """

    # Stage the commands every 1 second.
    body = "parallel -j {num_cores_simul} << EOF_PARALLEL\n"
    body = body.format(num_cores_simul=num_cores_simul)
    if silence:
        redirect = "&> /dev/null"
    else:
        redirect = ""
    for i, line in enumerate(script_lines):
        new_line = line.rstrip() + redirect + "\n"
        if i < num_cores_simul:
            new_line = "sleep {i}; ".format(i=i) + new_line
        body = body+new_line
    body += "EOF_PARALLEL\n"
    return body