UNX_ISUID
attribs[3] = (xattr & UNX_ISUID)? 's' : 'x';
attribs[3] = (xattr & UNX_ISUID)? 'S' : '-'; /* S = undefined */
attribs[3] = (xattr & UNX_ISUID)? 's' : 'x';
attribs[3] = (xattr & UNX_ISUID)? 'S' : '-'; /* S==undefined */