From the NannyMUD documentation

LAST CHANGE

2004-02-15

FUNCTION

NAME
        valid_name - check that the name is a valid player name


SYNTAX
        int valid_name(string name, object user, int silent).

LOCATION
        /obj/support

DESCRIPTION
        This function checks that the given name is a valid player
        name. The checks are:
        - the name can be at most 11 characters long
        - the name can only contain letters a-z

        The argument 'user' is the user who gets the messages from the
        checks. The messages can be turned off using the argument
        'silent'.

        The function returns 0 (zero) for invalid names, and one (1)
        for valid names.