External triggers from runcommand-onstart.sh

[Rens]

X86_64 - Ubuntu Server 24.04.2 LTS
Script version 4.8.9

I'll preface this with I am my worst enemy and I am probably over reaching in my capabilities, I am by no means a programmer but can work with python files.

Reding the various posts a lot of things can be done with runcommand-onstart.sh and I have Ideas.
And I set up a 2nd retropie to experiment... without stuffing too much up.

I get there are multiple variables onstart.sh uses as per: https://retropie.org.uk/forum/post/23378

To see what they produce can I (for example):

echo $rom > ~/test.txt

To then later use these outputs in a command for an external program?

[mitu]

@Rens said in External triggers from runcommand-onstart.sh:

To then later use these outputs in a command for an external program?

Not sure what that means - perhaps you'd better explain what you'd like to accomplish during the onstart phase ?

[Rens]

@mitu Sorry for the delayed reply...

The plan is to drive an LED matrix, not unlike pixelcade has done, but from scratch.
I'm running rpi-rgb-led-matrix on a raspberry pi-zero currently separately from the retro-pie.

Onstart I want to run a script, that ssh into the pi-zero and runs led-image-viewer with art based on the rom file or if no art found a default image for system/emulator

So as i understand it I need to see what the variable contains to then tie it to an image.

[mitu]

@Rens said in External triggers from runcommand-onstart.sh:

Onstart I want to run a script, that ssh into the pi-zero and runs led-image-viewer with art based on the rom file or if no art found a default image for system/emulator

Alright, though I don't see the connection with the output part.

Regardless, you can run your scripts from the onstart event handlers and they can do everything a script can, including writing files with variables received by the onstart handler (ROM file, SYSTEM, etc.)

[sleve_mcdichael]

@Rens I think you're asking what parameters are passed to the onstart/onend scripts. It is just the four mentioned in the docs: $1 = system, $2 = emulator, $3 = rom path and $4 = command

https://retropie.org.uk/docs/Runcommand/#runcommand-scripts

Useful data are passed as arguments to these scripts:

• $1 - the system (eg: atari2600, nes, snes, megadrive, fba, etc).
• $2 - the emulator (eg: lr-stella, lr-fceumm, lr-picodrive, pifba, etc).
• $3 - the full path to the rom file.
• $4 - the full command line used to launch the emulator.

You can see here, for example, the runcommand-onstart.sh and others are called with the user_script function:

    user_script "runcommand-onstart.sh"

The function:

https://github.com/RetroPie/RetroPie-Setup/blob/cdb2bda29fab4cae57ca5bf283f87620ab4be851/scriptmodules/supplementary/runcommand/runcommand.sh#L1300

# calls script with parameters SYSTEM, EMULATOR, ROM, and commandline
function user_script() {
    local script="$CONFIGDIR/all/$1"
    if [[ -f "$script" ]]; then
        bash "$script" "$SYSTEM" "$EMULATOR" "$ROM" "$COMMAND" </dev/tty 2>>"$LOG"
    fi
}

The meat is here:

        bash "$script" "$SYSTEM" "$EMULATOR" "$ROM" "$COMMAND" </dev/tty 2>>"$LOG"

As you can see, only the four parameters "$SYSTEM" "$EMULATOR" "$ROM" "$COMMAND" are passed to $script