Problem with popen on windows

ruby-talk
1

Hmm, this has no effect on the backqoutes thingie. It has an effect on
popen but whatever I put in COMSPEC it just stops working.

C:\WINNT\system32\cmd.exe is the standard, i tried:

C:\WINNT\system32\command.com
C:\WINNT\system32\cmd.exe /MIN
and empty

all have the same effect: no window poping up (fine) but no process is
executed also (not so fine)

why is cmd.exe started anyway?

cheers

Simon

···

From: Robert Klemme [mailto:bob.news@gmx.net]

Kroeger Simon (ext) wrote:
> Hi all,
>
> i'm using ruby 1.8.2 (2004-12-25) [i386-mswin32] on win2000.
>
> When starting my GUI app with rubyw (because i don't like the empty
> window) there is another window poping up whenever i call popen. (or
> use backquotes to start another process)
>
> Using just ruby.exe all seems fine (except the initial nasty empty
> window)
>
> Someone knows a way around?

Untested: maybe you can change COMSPEC env var in your ruby script to
point to another binary that won't open a window before
executing the new
process. Another option might be to add a command line param
to COMSPEC -
although I don't know whether that would work.

Kind regards

    robert

2

I too would dearly love to find a solution to this. I have seen this question
batted about several times over the years, but no solution.

I don't know cmd.exe is invoked, but presume it acts as the shell for system()
``() and popen(). The relevant lines in win32/win32.c in the Ruby source
seem to be in CreateChild (caution: IANA C-programmer)

  else if ((shell = getenv("COMSPEC")) &&
     ((redir < 0 ? has_redirection(cmd) : redir) ||
      isInternalCmd(cmd, shell))) {
      char *tmp = ALLOCA_N(char, strlen(shell) + len + sizeof(" /c "));
      sprintf(tmp, "%s /c %.*s", shell, len, cmd);
      cmd = tmp;
  }

Looking at this code and the cmd.exe reference at
www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/cmd.mspx

it seemed worth trying
ENV['COMSPEC'] += ' /q'
in Ruby to see if switching cmd.exe's echo off would suppress the annoying
box pop-up. But having done this, any system, ``, popen call then fails
with ENOENT - as if Windows can't then locate the shell executable.

Using command.com works for me, but still shows a pop-up box, and I
can't see any suitable options to suppress it.

I'm stumped from here, but perh someone with a better knowledge of
Windows process internals and/or Ruby internals can help.

alex

Kroeger Simon (ext) wrote:

···

Hmm, this has no effect on the backqoutes thingie. It has an effect on
popen but whatever I put in COMSPEC it just stops working.

C:\WINNT\system32\cmd.exe is the standard, i tried:

C:\WINNT\system32\command.com
C:\WINNT\system32\cmd.exe /MIN
and empty

all have the same effect: no window poping up (fine) but no process is
executed also (not so fine)

why is cmd.exe started anyway?

cheers

Simon

From: Robert Klemme [mailto:bob.news@gmx.net]

Kroeger Simon (ext) wrote:

Hi all,

i'm using ruby 1.8.2 (2004-12-25) [i386-mswin32] on win2000.

When starting my GUI app with rubyw (because i don't like the empty
window) there is another window poping up whenever i call popen. (or
use backquotes to start another process)

Using just ruby.exe all seems fine (except the initial nasty empty
window)

Someone knows a way around?

Untested: maybe you can change COMSPEC env var in your ruby script to
point to another binary that won't open a window before executing the new
process. Another option might be to add a command line param to COMSPEC -
although I don't know whether that would work.

Kind regards

   robert