Re: Bug: babel: results switch (output vs. value) has no or wrong effect for sh source block [7.7 (release_7.7.107.g7a82)]

[Michael Brand <michael.ch.brand@gmail.com>]

Hi Eric

2011/8/20 Eric Schulte <schulte.eric@gmail.com>:
> [...] I would lean towards thinking
> that passing along error messages is more important than returning error
> codes, but if the community thinks differently I'm happy to change the
> ob-sh behavior.

A non-zero exit status and stderr of a process are not necessarily
related. Because a process may also use
- a non-zero exit status without error situation (e. g. grep, diff)
- stderr for output not related with errors
- stdout for error messages
I would like very much to be able to collect all available feedback
from a process at the same run. Even with an optional indication of
the origin, for ambiguity like the "hello" below or just for clarification.

> Unfortunately it seems that in either case the sh code blocks will need
> to be different than other languages either in its handling of errors or
> of return values.  This is unavoidable due to the overloading of return
> values in the shell as error indicators.

If the shell is a special case for babel anyway, why not something
like the following?

#+begin_src sh :exports stdout stderr exit_status -v
  echo hello
  echo hello >&2
  false
#+end_src

#+results:
: 2: hello
: 1: hello
: exit status: 1

This would have been
- with an option -v for verbosity to prefix
  stdout with "1: ", stderr with "2: " and the exit status
- with the exit status of the last command without the need of an
  extra "echo $?".

My habit as a background info: To learn more from the shell I use
- a shell prompt with the exit status of the last command
- when I sometimes want to visually divide stdout and stderr (bash):
  { { echo hello; echo hello >&2; } 3>&1 1>&2 2>&3 | sed 's/^/2: /'; } \
      3>&1 1>&2 2>&3 | sed 's/^/1: /'; 3>&-
  to output:
  2: hello
  1: hello

Michael