From: Name Name <exl2@...>
Date: 2006-07-12T05:14:03+09:00
Subject: Re: Processes and Portability

I want this to be portable, ie not just *nix, so I can't fork.  However, 
I am doing something similar to forking in terms of getting the pid 
which popen will do.  I'm sure if I used fork (which I can't) on program 
> logfile, it won't be the pid of program (or it might be, i'm not sure, 
but the point is, the logic is messed up since I am doign the extra 
redirecting)

Yohanes Santoso wrote:
> Name Name <exl2@cornell.edu> writes:
> 
>> a=IO.popen("program > logfile"), but on Windows this creates two 
>> processes, cmd.exe and program.  a.pid only gives the pid of cmd.exe. 
>> And the behavior on *nix seems to be just the program (although I can be 
>> wrong).
> 
> The behaviour in *nix depends on your /bin/sh. Some shells gives the
> child's pid, other gives the pid of itself.
> 
> pdksh gives the pid of itself.
> bash gives the pid of the child (the behaviour you wanted).
> Don't know about other shells.
> 
> The lesson here, you can't get the pid of the child consistently
> unless you do the forking yourself.
> 
> YS


I know that Harmen.  I want the pid of not the intermediate shell, which 
is the one I am getting back with popen.  I want the pid of the program 
itself that I opened.  Also, program does produce output and logfile is 
writeable, and I need this to run on any system.

>On Linux that should work if program 'progam_name' produces output and 
>file 'logfile' is writable. One of the two processes you mentioned is an 
>intermediate shell by the way.

>Harmen

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