Blank first line in a tangled file prevents src block execution

Blank first line in a tangled file prevents src block execution

[Leo Alekseyev]

I have the following source block that I tangle to produce a short script:

#+begin_src sh :tangle code/get_wavs.sh
  #!/bin/bash
  for fn_in in "$@"; do
      fn_out=$(sed -e 's|\.3gp$||g' -e 's|$|.wav|g' <<< $fn_in)
      ffmpeg -i $fn_in -vn -f wav -acodec pcm_u8 $fn_out
  done
#+end_src

However, the tangled file has a blank first line.  As a result, I
can't seem to run this script either using sh -c, or by putting it
inside a code block.  In other words, the following line fails:

sh -c "code/test.sh data/salsa/20120308_av_jc/song2/*.3gp"
code/test.sh: 4: Syntax error: redirection unexpected

And, similarly, this fails

#+begin_src sh
  code/get_wavs.sh data/salsa/20120308_av_jc/song2/*.3gp
#+end_src


On the other hand, the script runs fine from the command line, or from
an org-mode shell: link, i.e. just running

code/test.sh data/salsa/20120308_av_jc/song2/*.3gp

at bash prompt produces the desired result.


I am not sure what the rules are about blank lines before the
hash-bang directive in Bash, and why in particular the blank line
seems to cause sh -c ... and orb-babel src execution to break, but the
current behavior seems broken.

Re: Blank first line in a tangled file prevents src block execution

[Nick Dokos]

Leo Alekseyev <dnquark@gmail.com> wrote:

> I have the following source block that I tangle to produce a short script:
> 
> #+begin_src sh :tangle code/get_wavs.sh
>   #!/bin/bash
>   for fn_in in "$@"; do
>       fn_out=$(sed -e 's|\.3gp$||g' -e 's|$|.wav|g' <<< $fn_in)
>       ffmpeg -i $fn_in -vn -f wav -acodec pcm_u8 $fn_out
>   done
> #+end_src
> 
> However, the tangled file has a blank first line.  As a result, I
> can't seem to run this script either using sh -c, or by putting it
> inside a code block.  In other words, the following line fails:
> 

Add ":padline no"

Nick

Re: Blank first line in a tangled file prevents src block execution

[Eric Schulte]

Nick Dokos <nicholas.dokos@hp.com> writes:

> Leo Alekseyev <dnquark@gmail.com> wrote:
>
>> I have the following source block that I tangle to produce a short script:
>> 
>> #+begin_src sh :tangle code/get_wavs.sh
>>   #!/bin/bash
>>   for fn_in in "$@"; do
>>       fn_out=$(sed -e 's|\.3gp$||g' -e 's|$|.wav|g' <<< $fn_in)
>>       ffmpeg -i $fn_in -vn -f wav -acodec pcm_u8 $fn_out
>>   done
>> #+end_src
>> 
>> However, the tangled file has a blank first line.  As a result, I
>> can't seem to run this script either using sh -c, or by putting it
>> inside a code block.  In other words, the following line fails:
>> 
>
> Add ":padline no"
>

Or try

#+begin_src sh :tangle code/get_wavs.sh :shebang #!/bin/bash
  for fn_in in "$@"; do
      fn_out=$(sed -e 's|\.3gp$||g' -e 's|$|.wav|g' <<< $fn_in)
      ffmpeg -i $fn_in -vn -f wav -acodec pcm_u8 $fn_out
  done
#+end_src

-- 
Eric Schulte
http://cs.unm.edu/~eschulte/

Re: Blank first line in a tangled file prevents src block execution

[Nick Dokos]

Eric Schulte <eric.schulte@gmx.com> wrote:

> Or try
> 
> #+begin_src sh :tangle code/get_wavs.sh :shebang #!/bin/bash
>   for fn_in in "$@"; do
>       fn_out=$(sed -e 's|\.3gp$||g' -e 's|$|.wav|g' <<< $fn_in)
>       ffmpeg -i $fn_in -vn -f wav -acodec pcm_u8 $fn_out
>   done
> #+end_src
> 

That reminds me: I believe shebang is used in tangling, but not in evaluation.
Assuming that's correct, is there any fundamental reason for it not being used
in evaluation?

Panruo Wu's question in another thread ( http://thread.gmane.org/gmane.emacs.orgmode/53157 )
brought this to mind.

Thanks,
Nick

Re: Blank first line in a tangled file prevents src block execution

[Eric Schulte]

Nick Dokos <nicholas.dokos@hp.com> writes:

> Eric Schulte <eric.schulte@gmx.com> wrote:
>
>> Or try
>> 
>> #+begin_src sh :tangle code/get_wavs.sh :shebang #!/bin/bash
>>   for fn_in in "$@"; do
>>       fn_out=$(sed -e 's|\.3gp$||g' -e 's|$|.wav|g' <<< $fn_in)
>>       ffmpeg -i $fn_in -vn -f wav -acodec pcm_u8 $fn_out
>>   done
>> #+end_src
>> 
>
> That reminds me: I believe shebang is used in tangling, but not in evaluation.
> Assuming that's correct, is there any fundamental reason for it not being used
> in evaluation?
>

Shell code blocks are evaluated using the org-babel-sh-command variable.
When the executing command is explicitly provided there is no need for a
shebang line, and it would be (to my knowledge) ignored.

Best,

-- 
Eric Schulte
http://cs.unm.edu/~eschulte/