[rrd-developers] Re: BUG: attempt to put segment in horiz list twice ??

Ruud H.G. van Tol rvtol at isolution.nl
Wed Jul 27 18:32:08 MEST 2005

Per Jessen:

> [system()]
> when I use "rrdtool graph -"

I read news://news.gmane.org/gmane.comp.db.rrdtol.user later
and saw how you use rrdtool.

> The code that produces good PNGs but make the browser hang:
>         oldstdout=dup(1);       // take a copy of stdout
>         oldstderr=dup(2);
>         dup2(s,1);              // make stdout = s
>         close(2);               // close stderr
>         system(buffer);         // call rrdtool to do the biz.
>         dup2(oldstdout,1);      // restore stdout.
>         dup2(oldstderr,2);

You shouldn't close stderr, but redirect it somewhere, like to a file or
to /dev/null.
Is the command-string in 'buffer' properly terminated with a 0-byte?

Or *maybe*, as an alternative way to restore stderr, leave all that code
as is, but replace the line with "dup2(oldstderr,2);" by:


which I copied from:

>> In a system() call, you can append " 2>$tmpfile" to the commandline.
> Yeah, I did think of that too - I'll have to try it again, but I
> think it produced the same result (browser hangs).

Do a test with "rrdtool graph - 2>/dev/null"
and also test "2>/dev/null rrdtool graph -"

Which shell do you use?

Grtz, Ruud

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