set-multiple-wallpapers.sh

#!/bin/bash

# ====================================================================== #
# Created on Linux Mint 22.3 "zena" - Cinnamon Edition                   #
# ====================================================================== #
#                                                                        #
# > required installs (sudo apt install ...)                             #
#                                                                        #
#   xrandr                                                               #
#                                                                        #
#   xwallpaper                                                           #
#                                                                        #
#                                                                        #
# > use xrandr --query to get connected displays and their identifiers   #
#                                                                        #
#   example output:                                                      #
#                                                                        #
#       DP-3 connected primary 1920x1080+1920+0 ...                      #
#                                                                        #
#       HDMI-0 connected 1920x1080+0+0 ...                               #
#                                                                        #
# > only edit sections below with asterisks (*) in comment               #
#                                                                        #
# ====================================================================== #


# ******** define background image / wallpaper path(s) ********

WALLPAPERS=(
    "/<path>/<to>/<image>/<file1.jpg>"
    "/<path>/<to>/<image>/<file2.png>"
)

# ******** do not edit beyond this point **********************


# checks dependencies; do not edit unless you know what you're doing

command -v xrandr >/dev/null 2>&1 || { echo "xrandr not installed: use 'sudo apt install x11-xserver-utils' then try again."; exit 1; }

command -v xwallpaper >/dev/null 2>&1 || { echo "xwallpaper not installed: use 'sudo apt install xvallpaper' then try again"; exit 1; }


# display environ safety fallback - set DISPLAY only if not already defined; probably not needed in most cases but can be for systemd, cron, or early boot exec

export DISPLAY="${DISPLAY:-:0}"


# If XAUTHORITY is not set but .Xauthority exists, define it

if [[ -z "$XAUTHORITY" && -f "$HOME/.Xauthority" ]]; then
    export XAUTHORITY="$HOME/.Xauthority"
fi


TIMER=0

TIMEOUT=30

# Initial check for connected displays

mapfile -t DISPLAYS < <(xrandr --query | grep " connected" | awk '{print $1}')


# if primary display not yet recognized, wait 1 second and loop

while [ ${#DISPLAYS[@]} -eq 0 ]; do
    
    ((TIMER+=1))

    # if timeout reached, exit.
    if ((TIMER >= TIMEOUT )); then
        echo "Script timed out - monitor not detected."
        exit 1
    fi

    # Refresh the list of connected displays
    mapfile -t DISPLAYS < <(xrandr --query | grep " connected" | awk '{print $1}')

    sleep 1

done


# loop length safety; will only loop as many times as it the smallest length array; basically a min() function

LOOP_LIMIT=$(( ${#DISPLAYS[@]} < ${#WALLPAPERS[@]} ? ${#DISPLAYS[@]} : ${#WALLPAPERS[@]} ))


# assign each id to a variable below (create more if necessary)

for ((i=0; i<LOOP_LIMIT; i++)); do
    xwallpaper --output "${DISPLAYS[$i]}" --zoom "${WALLPAPERS[$i]}"
done