Dynamic IP address for org babel ssh dir param

Question

I use this in emacs to connect and execute commands remotely:

#+BEGIN_SRC sh :dir /ssh:app_user@34.143.149.84:/tmp
pwd
#+END_SRC

#+RESULTS:
: /tmp

Recently, people have gone "cloud scaling" so the IP address 34.143.149.84 changes often.

The IP address can be determined by this bash:

sentinel list staging | grep InService | ruby -ne '$_=~/\A  (.*?) /; puts $1' | tail -n 1

How can I modify the header

+BEGIN_SRC sh :dir /ssh:app_user@34.143.149.84:/tmp

to dynamically determine the IP address.

Answer 1

Assuming that your bash script only puts out the ip, you could use the following function:

(defun get-ssh-ip ()
  "Query the ip address and return the result as value for sh block header option :dir."
  (let ((ip (shell-command-to-string "sentinel list staging | grep InService | ruby -ne '$_=~/\A  (.*?) /; puts $1' | tail -n 1")))
    (format "/ssh:app_user@%s:/tmp" ip)))

And use it in your org files:

#+header: :exports both
#+header: :results output
#+BEGIN_SRC sh :dir (get-ssh-ip)
pwd
#+END_SRC