Post History

Capture separate _and_ combined stdout/stderr

Using BASH, how can I redirect stdout and stderr each, to two separate files, simultaneously?

That's a mouthful, let me clarify a little:

I have a hypothetical script that may/will generate output on both stdout and stderr.  I want to run the script and wind up with three output files:

1. The contents of stdout only (`>stdout.txt`).
2. The contents of stderr only (`2>stderr.txt`).
3. The combined contents of stdout and stderr, interleaved as they would have been had they been printed to the terminal in real time (`>both.txt 2>both.txt`).

With Zsh you can do something like this with `MULTIOS` enabled:

```
script.txt >stdout.txt >>both.txt 2>stderr.txt 2>>both.txt
```

...but I need something that'll work on systems that don't have Zsh installed.