rewrite relative or absolute path from inherited tramp ssh property with org-babel

Question

I define a global remote session for all my sh block code with properties

:PROPERTIES
:HEADER-ARGS:bash: :dir /ssh:xxx@myvm:/home/xxx/
:END:

In my other bash blocks, I inherit this property, but after working folder was created, my code are executed in sub folder of /home/xxx

Here an example with creation of two folders in /home/xxx : todolist1 and todolist2

I finally found that noweb is a good path to follow :

* Example
:PROPERTIES:
:HEADER-ARGS:bash: :dir /ssh:xxx@myvm:/home/xxx/
:END:

#+NAME: createdir
#+BEGIN_SRC bash :var folder="" :exports none
if [ -n "${folder}" ] ; then
    if [ -d "${folder}" ]; then
        rm -Rf "${folder}"
    fi
    mkdir "${folder}"
fi
#+END_SRC

#+NAME: gotodir
#+BEGIN_SRC bash :var folder="" :exports none
if [ -n "${folder}" ] ; then
    cd "${folder}"
fi
#+END_SRC

#+BEGIN_SRC bash :var folder="todolist1" :noweb yes :exports both
<<createdir>>
#+END_SRC

#+BEGIN_SRC bash :var folder="todolist2" :noweb yes :exports both
<<createdir>>
#+END_SRC

// First action on todolist 1
#+NAME: addmytodolist1
#+BEGIN_SRC bash :var folder="todolist1" :noweb yes :exports both :results verbatim
<<gotodir>>
cat > todolist1.org <<EOF 
#mytodolist
- [ ] item 1
- [X] item 2
EOF
#+END_SRC

// Second action on todolist 1
#+NAME: addmytodolist12
#+BEGIN_SRC bash :var folder="todolist1" :noweb yes :exports both :results verbatim
<<gotodir>>
cat >> todolist1.org <<EOF 
- [ ] item 3
EOF
#+END_SRC

// First action on todolist 2
#+NAME: addmytodolist2
#+BEGIN_SRC bash :var folder="todolist2" :noweb yes :exports both :results verbatim
<<gotodir>>
cat > todolist2.org <<EOF 
- [X] item 1
- [X] item 2
- [ ] item 3
- [X] item 4
EOF
#+END_SRC

To write less verbose and better maintainable code, i try without success :

• to hide the <<gotodir>> instruction from export using :prologue <<gotodir>> => failed

• I also try to directly expand dir: into header args, but that doesn't take in account the remote TRAMP ssh connexion : #BEGIN_SRC sh :var folder="todolist1" :dir (expand-file-name (org-sbe "gotodir"))

• I suppose it exist some elisp code to get TRAMP ssh folder, and rewrite it/overwrite it by using new url {trampfolder}/todolist1 or {trampfolder}/todolist2 ?

There are probably better and more robust way to do that, I'm interested to know what org-mode/org-babel guru :) !

Answer 1

Use elisp in the :dir header to fetch the value the :HEADER-ARGS:bash from the PROPERTIES drawer, remove original :dir string and return new value with a subdirectory appended.

• For example, to append the todolist1, subdirectory, set the header below on the bash code block.

  :dir (format "%s/todolist1" (replace-regexp-in-string ":dir +" "" (org-entry-get nil "HEADER-ARGS:bash" t)))
  

Below is an full example, which executes 3 bash code blocks via tramp in the default, todolist1, and todolist2 directories.

* Example
:PROPERTIES:
:HEADER-ARGS:bash: :dir /ssh:xxx@myvm:/home/xxx
:END:

- The block below will execute in =/ssh:xxx@myvm:/home/xxx=, i.e. the default =:dir=

  #+BEGIN_SRC bash 
  echo "$USER@$HOSTNAME executed this block in the $PWD directory"
  #+END_SRC

  #+RESULTS:
  : xxx@myvm executed this block in the /home/xxx directory

- The block below will execute in =/ssh:xxx@myvm:/home/xxx/todolist1=

  #+BEGIN_SRC bash :dir (format "%s/todolist1" (replace-regexp-in-string ":dir +" "" (org-entry-get nil "HEADER-ARGS:bash" t)))
    echo "$USER@$HOSTNAME executed this block in the $PWD directory"
  #+END_SRC

  #+RESULTS:
  : xxx@myvm executed this block in the /home/xxx/todolist1 directory

- The block below will execute in =/ssh:xxx@myvm:/home/xxx/todolist2=

  #+BEGIN_SRC bash :dir (format "%s/todolist2" (replace-regexp-in-string ":dir +" "" (org-entry-get nil "HEADER-ARGS:bash" t)))
    echo "$USER@$HOSTNAME executed this block in the $PWD directory"
  #+END_SRC

  #+RESULTS:
  : xxx@myvm executed this block in the /home/xxx/todolist2 directory

---

The noweb functionality built into org-mode is amazingly useful!

• Assign names to SRC blocks using #+NAME: or :new-ref headers.

  e.g. #+NAME: my-code or :noweb-ref my-code

• SRC blocks with the same name become a single block when read in order from the top to bottom of the org file.

• Names provide 2 new features inside other SRC blocks with the :noweb yes header.

  • Use <<my-code>> syntax to automatically embed code from blocks named my-code.

  • Use <<my-code()>> syntax to execute blocks named my-code and automatically embed the #+RESULTS: generated by the named block. As extra bonus, you can pass variables in the the () to the named blocks before execution.

• Use the :tangle and :file headers to generate multiple files out and org file. As an added bonus, use :mkdir yes to automatically create missing subdirectories.

• Mix and match these features to generate source code, config files, images and other forms human documentation from an org-mode file. In the past, I have generated 100+ customized files to build a project from a single org file.

Thanks for asking your question!

---

The code in this answer was tested using:
emacs version: GNU Emacs 25.2.1 (x86_64-unknown-cygwin, GTK+ Version 3.22.10)
org-mode version: 9.1.2