Piping a .cfg into SU2 | Hot-Swapping .cfg option in general

[TobiKattmann]

Hi all,

I want to add a config option to an existing .cfg file and pipe that into SU2 without explicitly creating the concatenated file. So the naive approach would be (with Quickstart):
cat inv_NACA0012.cfg <(echo "SCREEN_WRT_FREQ_INNER= 10") | SU2_CFD
The cat part does its job. The follwoing also works as intended:
cat inv_NACA0012.cfg <(echo "SCREEN_WRT_FREQ_INNER= 10") | grep SCREEN
that is, finding the append option without permanently adding it to inv_NACA0012.cfg.

I guess that is currently not possible as SU2 only reads the filename from stdin and not the file content. If we were to SU2_CFD < inv_NACA0012.cfg then the above shown method would prob work.

Now one could create a temporary file and delete later like so:
cat inv_NACA0012.cfg <(echo "SCREEN_WRT_FREQ_INNER= 10") > tmp.cfg && SU2_CFD tmp.cfg && rm tmp.cfg
which does the job but is not exactly pretty.

Is there another easy elegant way to do so?

Another thing is Hot-Swapping 🔥 options using e.g. sed (e.g SCREEN_WRT_FREQ_INNER=10 added to Quickstart prior to this command):
sed "s/SCREEN_WRT_FREQ_INNER.*/SCREEN_WRT_FREQ_INNER= 20/g" inv_NACA0012.cfg
and then piping the whole thing to SU2. So instead adding options changing them in-place. Again without creating a new file.

Why
Testing different values for config options is s.th. that we all do regularly and often enough one creates a new folder for each change because I want to compare results, right... and then foldernames happen: test -> test_ROE test_JST -> test_ROE_CFL5 test_ROE_CFL15 test_ROE_CFL50 -> test_ROE_CFL15_noLimiter -> test_ROE_CFL15_noLimiter_SA ... you know the drill (I hope so at least). All these changes are incremental (1 option at a time because you want to know when things blow up... or work for the first time 😄 ).
Here it would be awesome to just create an addtions.cfg or changes.cfg (for hot-swapping) and call that with the original cfg with the above desired logic. The original file could be symlinked still in the folder in question. I checked countless time in these kind of situations using diff/meld what I changed and if I changed maybe more than the folder-title suggests... Because I know me ... and past-me can't be trusted.

Now one can surely write chunky python stuff but I am sure there is a lightweight solution in bash making use of all those juicy command line tools and techniques.

I hope my rough goal is understandable and feel free to hit me with different solutions for this "incremental-option-change" problem.

[pcarruscag]

You can use the FADO framework for that kind of parametric sweep, I do it as part of my optimization all the time.
I think the challenge with piping files in would be the multi config format.
TBH I would not use this kind of hot-swapping very often, I know at some point I would forget which settings I used for each run.