Michael Brand <michael.ch.br...@gmail.com> writes:
> Hi Eric
>
> 2011/8/20 Eric Schulte <schulte.e...@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.
>
I agree that some mechanism for collecting output from STDERR could be
useful, however its implementation would not be trivial.
>
>> 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
>
I think that in general mixing the output status with STDOUT would not
be a clean solution, as it would require parsing to use. Also, I don't
think that the example above would help to bring the behavior of sh code
blocks more in-line with other code blocks.
Note that during interactive evaluation if the exit status is non-0 then
STDERR will be dumped into a babel error buffer which will be poped up,
so this information will not be silently discarded.
Best -- Eric
--
Eric Schulte
http://cs.unm.edu/~eschulte/
