Convert user name to a uid

    user
        user name to convert to its uid

    CLI Example:

    .. code-block:: bash

        salt '*' file.user_to_uid root

def user_to_uid(user):
    '''
    Convert user name to a uid

    user
        user name to convert to its uid

    CLI Example:

    .. code-block:: bash

        salt '*' file.user_to_uid root
    '''
    if user is None:
        user = salt.utils.user.get_user()
    try:
        if isinstance(user, int):
            return user
        return pwd.getpwnam(user).pw_uid
    except KeyError:
        return ''