<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:

def _parse(contents=None, file_name=None):
    '''
    Parse a standard pam config file
    '''
    if contents:
        pass
    elif file_name and os.path.exists(file_name):
        with salt.utils.files.fopen(file_name, 'r') as ifile:
            contents = salt.utils.stringutils.to_unicode(ifile.read())
    else:
        log.error('File "%s" does not exist', file_name)
        return False

    rules = []
    for line in contents.splitlines():
        if not line:
            continue
        if line.startswith('#'):
            continue
        control_flag = ''
        module = ''
        arguments = []
        comps = line.split()
        interface = comps[0]
        position = 1
        if comps[1].startswith('['):
            control_flag = comps[1].replace('[', '')
            for part in comps[2:]:
                position += 1
                if part.endswith(']'):
                    control_flag += ' {0}'.format(part.replace(']', ''))
                    position += 1
                    break
                else:
                    control_flag += ' {0}'.format(part)
        else:
            control_flag = comps[1]
            position += 1
        module = comps[position]
        if len(comps) > position:
            position += 1
            arguments = comps[position:]
        rules.append({'interface': interface,
                      'control_flag': control_flag,
                      'module': module,
                      'arguments': arguments})
    return rules