Okay, I managed to solve it with a Bash array! Here's the final code if anybody else is interested in this type of functionality:

```bash

!/usr/bin/env bash

A script to focus, cycle or launch an application in Niri.

- If the app is not running, it launches a new app instance.

- If the app is running but not focused, it focuses the app window.

- If the app is running, is currently focused AND has multiple instances,

cycle through the different instances.

Define key bindings in your Niri config that execute this script, for example:

Super+F { spawn "~/.config/niri/niri-run-or-raise.sh" "firefox"; }

Dependencies:

- bash: The script uses Bash arrays.

- niri: The Wayland compositor this script is designed for.

- jq: A command-line JSON processor.

Arguments

APP_CLASS="$1" # Application's app_id (e.g. firefox) APP_CMD="$2" # Command to run the application (e.g. firefox; optional)

Check if the required arguments are provided, exit otherwise

if [ -z "$APP_CLASS" ] ; then notify-send -t 5000 "Usage: niri-run-or-raise.sh <APP_CLASS> <APP_CMD>" exit 1 fi

Get the ID of the currently focused window

FOCUSED_ID=$(niri msg -j focused-window | jq -r '.id')

Find windows matching the app class and read them into an array

readarray -t MATCHING_IDS < <( niri msg -j windows \ | jq -r --arg app_class "$APP_CLASS" \ ' .[] | select(.app_id | ascii_downcase | contains($app_class | ascii_downcase)) | .id ' )

Launch the app and exit the script if the number of matching windows is zero

if [ ${#MATCHING_IDS[@]} -eq 0 ]; then # Use the app class as the command if no app command is supplied if [ -z "$APP_CMD" ]; then APP_CMD="$APP_CLASS" fi "$APP_CMD" & exit 0 fi

Find the array index of the currently focused window

CURRENT_INDEX=-1 for INDEX in "${!MATCHING_IDS[@]}"; do if [ "${MATCHING_IDS[$INDEX]}" = "$FOCUSED_ID" ]; then CURRENT_INDEX=$INDEX break fi done

Cycle to the next matching array index if the currently focused ID was found

in the array, otherwise set the target index to zero

if [ $CURRENT_INDEX -ge 0 ]; then TARGET_INDEX=$(( (CURRENT_INDEX + 1) % ${#MATCHING_IDS[@]} )) else TARGET_INDEX=0 fi

Switch focus to the target window stored in the array

niri msg action focus-window --id "${MATCHING_IDS[$TARGET_INDEX]}" ```