Re: [Babel] Debugging shell code that misbehaves

[Dan Davison <davison@stats.ox.ac.uk>]

Sébastien Vauban <wxhgmqzgwmuf-geNee64TY+gS+FvcfC7Uqw@public.gmane.org>
writes:

> #+TITLE:     Debugging shell code that misbehaves
> #+DATE:      2010-10-14
> #+LANGUAGE:  en_US
>
> * Use case
>
> Let's say that:
>
> - This file is in =~/Client/Spec=
> - I'm working on such a chunk of code:
>
> #+begin_src sh :results output :exports results
> grep indAllocType ../Ontology/champs.csv |\
> iconv -f LATIN1 -t UTF8 |\
> tr "[]" "|" | cut -d "|" -f 2 | cut -d " " -f 2- |\
> sed 's%, %\n%g'
> #+end_src
>
> and that, when executing it, I've got an error with not enough context for me
> to understand what's the problem is.
>
> Sneak preview: under Cygwin, the =to= language (of the =iconv= command) must
> be =UTF-8= in the above case (with a dash).
>
> * Debug it
>
> So, in order to debug, I decide to add a =session= argument:
>
> #+begin_src sh :results output :exports results :session sva
> grep indAllocType ../Ontology/champs.csv |\
> iconv -f LATIN1 -t UTF8 |\
> tr "[]" "|" | cut -d "|" -f 2 | cut -d " " -f 2- |\
> sed 's%, %\n%g'
> #+end_src
>
> and, there, something totally different is occurring: =grep= is not finding
> the file anymore.
>
> Why? Because adding the session argument makes the code executed from my *home
> directory*, while it was executed from the *document's directory* in the first
> place.

Hi Seb,

This would be a bug. For me (ubuntu), the session does start up in the
document's directory. Perhaps the emacs shell session behaves
differently on your operating system (cygwin?)?

>
> So, this is not the right way to debug... as *conditions do change*.

but should not

>
> * Solution?
>
> What's the right solution for such a case?

Fix the bug. But failing that,

> - Putting a full path to the file =champs.csv= (instead of the relative one)
>   is not OK for me, as all of this is under SVN, and I want this to be
>   executable on someone's else PC (even if placed somewhere else).
>
> - Add an explicit =cd= to the right place, before the commands execute. Not
>   possible, for the same reason as above.

does it help to use a :dir header argument to specify default-directory
for the session?

Dan

>
> Is there some natural way to work around this?
>
> Best regards,
>   Seb