[mingw - C/C++] popen(): possible to "background" subprocess?

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By: lionelb

Greetings,

I am developing a program using MinGW/gcc on Win2k which pipes commands to Gnuplot
(http://www.gnuplot.info/). This works fine if I use popen() to open a pipe
to a subprocess running pgnuplot.exe (the Win32 pipe version of the Gnuplot
binary).

Problem is that is that as soon as my program terminates, so does the subprocess;
I would like to be able to keep the Gnuplot window open - i.e. keep the subprocess
running after termination of the parent process, much as the system() call does.

I can achieve this eg. under Cygwin, using fork(), pipe(), exec(), dup2(), ...
by exec-ing pgnuplot.exe as a background process (using "&" in the command line
passed to exec()).

Can I achieve the same under MinGW via popen(). I suspect I might be able to
using the Win32 _pipe(), _spawn(), etc., but there lies a world of pain...

Any ideas appreciated,

--
Lionel B



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[Michael Gerdau]

> I am developing a program using MinGW/gcc on Win2k which pipes commands to Gnuplot
> (http://www.gnuplot.info/). This works fine if I use popen() to open a pipe
> to a subprocess running pgnuplot.exe (the Win32 pipe version of the Gnuplot
> binary).
>
> Problem is that is that as soon as my program terminates, so does the subprocess;

AFAIK that's what popen() is supposed to do.

> I would like to be able to keep the Gnuplot window open - i.e. keep the subprocess
> running after termination of the parent process, much as the system() call does.

Then you probably have to do something like system()
(e.g. exec() and friends).

> I can achieve this eg. under Cygwin, using fork(), pipe(), exec(), dup2(), ...
> by exec-ing pgnuplot.exe as a background process (using "&" in the command line
> passed to exec()).
>
> Can I achieve the same under MinGW via popen().

I don't think so. It would be against what popen is supposed to do.
Under Cygwin you don't use popen to achieve that either (and there
is a reason ;-)

> I suspect I might be able to
> using the Win32 _pipe(), _spawn(), etc., but there lies a world of pain...

Since MinGW has no fork() I suppose the "world of pain" from above
is the way to go.

Hope you enjoy S&M ;-)
Michael
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