Thank you for your prompt response.

Yes that's right. The manual page is https://cinelerra-gg.org/download/CinelerraGG_Manual/Menu_Bar_Shell_Commands.html. After reading it, I realized that there was an example that I hadn't seen before.

So I compared and found my mistake. I replaced the call command "bash ~/Private/fab_guide/fab_guide-nos_videos/test.sh" by "~/Private/fab_guide/fab_guide-nos_videos/test.sh" and check "/path/script + argvs".
Now the call of this little test script works

I can now try to create a script that will make a copy of the snaps but in a smaller size.

First of all, let me remind you that any shell commands that you set up are logged in $HOME/.bcast5/Cinelerra_rc where all of your setup variables are kept.  So you may want to occasionally backup this file. It is kind of like your $HOME/.profile file for settings.

So the manual description you read is Menu Bar Shell Commands, I assume.  And you can see information about  RenderMux which I think you are using.  For this case the important thing to understand is that this depends on CIN_RENDER being defined within your session.  You got the error when you edited and checked the run box.  What the RenderMux command runs is in wherever you installed Cinelerra at:  ./doc/RenderMux.sh  .

I too get the error and have to try to remember how this works and then will respond more intelligently, hopefully.

I noticed that there is an option "run /path/script.sh + argvs" that would be useful for me.
So I searched in the manual but I didn't find a very precise explanation and no example.

To do a test I created a little bash script that simply reads the first argument and adds it to the test.txt file.

I create the shortcut in cinelerra with the command "bash ~/Private/fab_guide/fab_guide-nos_videos/test.sh" and I check run /path/script + argvs

At runtime, cinelerraGG returns "test: error exit status 32512".

How does this option work?