主要参考了水木清华BBS的代码，写得很丑，大家多多指点。
－－－
bbs.c
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添加两个函数的定义：
int new_flag_clearb(struct shortfile * bdcache)
{
        int rtnval;
        char bddir[STRLEN];
        setbdir(bddir, bdcache->filename);
        brc_initial(bdcache->filename);
        rtnval= flag_clearto(0, bddir, YEA);
        return rtnval;
}
int clear_all_new_flag()
{
        char ans[3],tmpcurbd[STRLEN];
        sprintf(genbuf,"确定要清除所有版面的未读标记? [Y/n]");
        getdata(t_lines-1,0,genbuf,ans, 2,DOECHO, YEA);
        if(ans[0]!='y'&&ans[0]!='Y')
                return 0;
        prints("  请稍等...");
        strncpy(tmpcurbd, currboard, STRLEN);
        currboard[0]='\0';
        tmpcurbd[STRLEN-1]=0;
        modify_user_mode(READING);  //修改用户状态是因为不是这个状态
                                        flag_clear_to不干活
        apply_boards(new_flag_clearb);
        modify_user_mode(MMENU);
        strcpy(currboard, tmpcurbd);
        return 1;
}

－－－－
comm_lists.c
---------
加上菜单的入口      
        {"GoodWish", sendgoodwish,0},
        {"ClrAllNFlg", clear_all_new_flag,0},
#ifdef ALLOWSWITCHCODE
        {"SwitchCode",switch_code,0},
#endif

－－－－
menu.ini
--------
修改菜单
@ExecBBSNet  0, 0, PERM_POST, "FBBSNet",    "(F) 网路连线"
@Dictionary  0, 0, PERM_POST, "Dictionary", "(D) 英汉/汉英字典"
@ClrAllNFlg  0, 0, PERM_POST, "Lclrnewflg", "(L) 清除全部未读标记"
@WinMine     0, 0, PERM_POST, "WinMine",    "(W) 扫雷游戏"
@Mary        0, 0, PERM_POST, "Mary",       "(M) 超级小玛丽"
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FROM 202.207.211.100