c/unix q

[Erez D]

On Thu, Jun 6, 2013 at 5:29 PM, E.S. Rosenberg <esr+linux-il at g.jct.ac.il>wrote:

> re:all, forgot to change my from field.
>
> 2013/6/6 Erez D <erez0001 at gmail.com>:
> >
> >
> >
> > On Thu, Jun 6, 2013 at 5:04 PM, E.S. Rosenberg <esr at g.jct.ac.il> wrote:
> >>
> >> 2013/6/6 Erez D <erez0001 at gmail.com>:
> >> >
> >> >
> >> >
> >> > On Tue, Jun 4, 2013 at 6:09 PM, Shachar Shemesh <shachar at shemesh.biz>
> >> > wrote:
> >> >>
> >> >> On 04/06/13 15:28, Erez D wrote:
> >> >>
> >> >> thanks,
> >> >>
> >> >> so i guess if i use unidirectional connection, and the reader does
> not
> >> >> expect to get an EOF()
> >> >> thank i'm safe.
> >> >>
> >> >> Why are you so keen on doing it wrong?
> >> >>
> >> >> No, you are not safe. If the child process dies because of a
> >> >> segmentation
> >> >> fault (or whatever), the parent will notice this through the EOF
> >> >> received (I
> >> >> am assuming here, since you couldn't be bothered with closing a file
> >> >> descriptor, that you did not install a SIGCHLD handler to monitor for
> >> >> this
> >> >> possibility). This means that should one process die unexpectedly,
> the
> >> >> other
> >> >> will hang forever.
> >> >
> >> > it's not a matter of being bothered. closing a file has it's
> >> > implications
> >> >
> >> > 1.  close the file for one thread closes for all
> >> thread and fork are 2 very different things, best practice for fork
> >> ('full' children, I think everyone understands fork() when you say
> >> child) is to close, when using threads that is I believe not the case.
> >> > 2. what if i want later children using the same pipe, as in all childs
> >> > write
> >> > to same pipe read by parent...
> >> so the children are all closing the read end and the parent only
> >> closes write, where is the problem?
> >
> > if the parent closes the "write" side, then new forked children have
> their
> > "write" side already closed.
> That's why we are able to check if we are a child or a parent with the
> fork() function.
>
that doesn't help

sunday: parent creates a pipe
monday: parent forks for child 1. parent closes write. child 1 closes read.
child 1 now can write and parent can read.
tuesday: parent forks for child 2. child 2 can not write - pipe already
close by parent on monday.


>  >>
> >> >
> >> >>
> >> >> Best practices are there for a reason, despite what others here might
> >> >> have
> >> >> you think.
> >> >>
> >> >> Shachar
> >> >
> >> >
> >> >
> >> > _______________________________________________
> >> > Linux-il mailing list
> >> > Linux-il at cs.huji.ac.il
> >> > http://mailman.cs.huji.ac.il/mailman/listinfo/linux-il
> >> >
> >
> >
>
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