Re: freopen on both stdout and stderr

Mark Bluemel wrote, On 23/11/07 12:01:
Guillaume Dargaud wrote:
Hello all,
a while ago I was pointed towards freopen as a way to redirect stderr to a log file. It works great, but apparently the app also writes a few lines to stdout. Now I could redirect to 2 separate files, but would rather keep the 2 flows together.

Is it correct to do this:
stderr=freopen(LogFile, "w", stderr);
stdout=freopen(LogFile, "a", stdout);

It's not in accordance with the standard to do this, as "stderr" and "stdout" are not, as I recall, guaranteed to be lvalues...

If you can assign them, and you're prepared to accept non-portability, then you could perhaps try the following, untested, hackery

stderr=freopen(LogFile, "w", stderr);
fclose(stdout);
stdout=stderr;

Otherwise, I'm not convinced you have many options available to you.

Personally I would use a mechanism outside the program in order to achieve this and not redirect either stdout or stderr within the program. E.g.
prog >log 2>&1
The precise mechanism (and whether it is even possible) is dependant on the system being used.
--
Flash Gordon
.

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