kern/149857: [kqueue] kqueue not reporting EOF under certain circumstances

Volodymyr Kostyrko c.kworr at
Tue Jul 10 15:02:56 UTC 2012

Konstantin Belousov wrote:
>> So you mean this is just my false assumption that EOF _should_ occur on
>> stdin? And it actually occurs only if source is a process which can send
>> EOF?
> 'Source' cannot be a process. Read filter on pipes can return EV_EOF.
> Read filter on vnodes (read: regular files) does not return EV_EOF,
> except in situation that is created by manual intervention of
> administrator.

This keeps me puzzled. How then I can tell that file at stdin is already 
at EOF? You mean I should treat stdin like normal vnode-backed file?

   off_t pos = 0, endpos;

   lseek(fileno(stdin), 0, SEEK_END);
   endpos = ftell(stdin);
   lseek(fileno(stdin), 0, SEEK_SET);

... and then later check it with:

       if(endpos != -1) {
         pos +=;
         if(pos >= endpos) {
           printf("end reached\n");

Is this a correct way to detect EOF? I'm letting besides that I should 
also detect vnode changes and update max file size accordingly.

> It should have been clear from my previous response.

Please excuse me, I'm a bit new to this things...

Sphinx of black quartz judge my vow.

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