Re: io.popen processes hanging around after close

[Ingo Struck <lua@...>]

Hello Rena,

On Mon, Oct 28, 2013 at 12:29:37PM -0400, Rena wrote:
> > On Mon, Oct 28, 2013 at 3:35 PM, Rena <hyperhacker@gmail.com> wrote:
> > > In my app I open a few processes using io.popen(), then read their output
> > > using posix.fileno() and posix.rpoll() to see if there's data available.
> > > When my app shuts down however (using os.exit(0)), even if I close the
> > > process file handles, they remain running in the background. How do I
> > > prevent this? I do both process:close() and posix.close(fd). (I found
> > > without the latter, the former would just hang...)
> >
> > You can either send a kill (posix.kill) signal to the child, or make
> > the child test to see if the pipe is still open - it depends if it is
> > doing anything or is blocked, and how much it is under your control.
> But how do I get the child's PID?

You can't using io.popen(). We had exactly the same problem
with io.popen and thus re-implemented it  (but that impl had
some other ugly quirks).

Try not to mix luaposix and standard system stuff.
You may want to use luaposix fork + pipe, cf.
http://luaposix.github.io/luaposix/docs/examples/fork.lua.html

HTH and kind regards

Ingo