Re: Lua fork concurrent processes

[Michal Kolodziejczyk <miko@...>]

On 05.11.2012 09:46, ms2008vip wrote:
>  
> Howdy:
>  
>          I want to execute background processes concurrently from a lua script 
> like :
>  
> a = io.popen("deploy.exp" .. ip1):read("*a")
> b = io.popen("deploy.exp" .. ip2):read("*a")
> ** 
> where a,b are continually running processes. When i do this as above, b will only run when a is finished. And the deploy.exp script is an expect script which
>  used to ssh few servers, and execute some commands. Then I need to fetch some text from a and b. Any idea on this? I tryed with the ExtensionProposal API. 


Do they really work "continually"? If so, you should not read all the
data, but just what is output. For example:

a=io.popen("deploy.exp" .. ip1)
b=io.popen("deploy.exp" .. ip2)
while a and b do
  if a then
    linea=a:read('*l)
    if not linea then
       a:close()
       a=nil
    end
    print('Got from a:', linea)
  end
  if b then
    lineb=b:read('*l)
    if not lineb then
       b:close()
       b=nil
    end
    print('Got from b:', lineb)
  end
end

Note that this still blocks on reading a line. I would use luasocket and
select() to resolve this, but the scripts then should use (TCP/UDP/Unix)
sockets instead of stdout.

Regards,
miko