imageSwitch.sh

#!/bin/bash

if test "$#" -eq 1; then
  echo 'Usage: $0 [path random]'
  echo ''
  echo 'path          Path where your backgrounds are stored. (Default: $HOME/.tilixBackgrounds)'
  echo 'random        true: Choose randomly a next image.'
  echo '              false: Iterate through images in folder. (Default)'
  echo ''
  echo 'No args starts script with defaults.'
  exit 1
fi

if test "$#" -ne 2; then
  # legacy support
  imagePath="$HOME/.tilixBackgrounds"
  randomMode="false"
else
  # parameter mode
  imagePath="$1"
  randomMode="$2"
fi

# Cron DBUS discovery block
# when used with cron or as global systemd service instead of user service, the following is needed to find the dbus of the current user
# change this to point to your specific UI session
# uiSession="gnome-session-b" # gnome
# uiSession="plasma_session" # plasma
# enable the following lines to find and export the DBUS address
# PID=$(pgrep "$uiSession")
# export DBUS_SESSION_BUS_ADDRESS=$(grep -z DBUS_SESSION_BUS_ADDRESS /proc/$PID/environ | tr '\0' '\n' | cut -d= -f2-)
# finally if used with cron do not forget to set up the cron job ;)

# start of the actual script
pics=("$imagePath"/*)
key="/com/gexperts/Tilix/background-image"
selected=$(dconf read $key)
echo "old: $selected"

if [ "$randomMode" = "true" ]
then
  numberPics=${#pics[@]}
  newIndex=$(($RANDOM % $numberPics))

  file="${pics[$newIndex]}"
else
  for ((i=0; i<${#pics[@]}; i++)); do
    if [ "'${pics[$i]}'" = "$selected" ]
    then
      file="${pics[0]}"

      if (($i+1<${#pics[@]}))
      then
        file="${pics[$i+1]}"
      fi
      break
    fi
  done
fi

echo "new: '$file'"
dconf write $key "'$file'"