[lxc-devel] create_run_template() - question

[Stéphane Graber]

On Sat, Dec 14, 2013 at 12:04:24PM +0200, Kevin Wilson wrote:
> Hello,
> Could anybody please explain:
> In  create_run_template() ,
> https://github.com/lxc/lxc/blob/master/src/lxc/lxccontainer.c
> 
> we have:
> 
>  if (quiet) {
>                         close(0);
>                         close(1);
>                         close(2);
>                         open("/dev/zero", O_RDONLY);
>                         open("/dev/null", O_RDWR);
>                         open("/dev/null", O_RDWR);
>                 }
> 
> Why do we need twice to call  open("/dev/null", O_RDWR) ? Is it have
> to do with running as daemon ? or is it redundant ?
> We don't use the returned fd in both cases.
> 
> Kevin

The code above closes the 3 standard fds:
 - 0 => stdin
 - 1 => stdout
 - 2 => stderr

And then re-opens them with correct values to hide any output from the
script.

So that line isn't redundant at all, if it was missing, I'd expect the
code to crash when something would try to write to stderr.

-- 
Stéphane Graber
Ubuntu developer
http://www.ubuntu.com
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