macOS Automator / Folder Actions Script to mount, move and automatically trash .dmg files

delete_dmg_after_use.sh

#!/bin/bash

# Configuration file path
CONFIG_FILE="$HOME/.dmg_script_config"

# Function to setup configuration
setup_configuration() {
  echo "Setting up configuration..."
  read -r -p "Enter the destination path [$HOME/Applications]: " DESTINATION
  DESTINATION=${DESTINATION:-$HOME/Applications} # Default to $HOME/Applications if input is empty

  read -r -p "Enter the log file path [$HOME/dmglogfile.log]: " LOG_FILE
  LOG_FILE=${LOG_FILE:-$HOME/dmglogfile.log} # Default to $HOME/dmglogfile.log if input is empty

  # Save to config file with proper quoting for paths
  echo "DESTINATION=\"$DESTINATION\"" > "$CONFIG_FILE"
  echo "LOG_FILE=\"$LOG_FILE\"" >> "$CONFIG_FILE"
  echo "Configuration saved to $CONFIG_FILE"
  echo "Setup completed successfully."
  exit 0 # Explicitly exit after setup
}

# Function to log messages
log() {
  # Ensure LOG_FILE is defined. If not, default to a temporary log file.
  local log_file="${LOG_FILE:-/tmp/dmg_script_temp.log}"
  mkdir -p "$(dirname "$log_file")" # Ensure the log directory exists
  echo "$(date '+%Y-%m-%d %H:%M:%S'): $1" >> "$log_file"
}

# Function to load and validate configuration
load_and_validate_configuration() {
  if [ ! -f "$CONFIG_FILE" ] || [ ! -s "$CONFIG_FILE" ]; then
    log "Configuration file not found or empty. Please run the script with --setup to configure."
    echo "Configuration file not found or empty. Please run the script with --setup to configure."
    exit 1
  fi
   
  # shellcheck source=/dev/null
    source "$CONFIG_FILE"
    log "INFO Configuration file loaded successfully."
    
  if [ -z "$DESTINATION" ] || [ ! -d "$DESTINATION" ]; then
    log "Error: Destination is not set or does not exist. Please re-run with --setup."
    echo "Error: Destination is not set or does not exist. Please re-run with --setup."
    exit 1
  fi

  if [ -z "$LOG_FILE" ]; then
    log "Error: Log file path is not set. Please re-run with --setup."
    echo "Error: Log file path is not set. Please re-run with --setup."
    exit 1
  fi
}

# Helper function for cleanup
cleanup() {
  if [ -n "$MOUNT_POINT" ]; then
    if ! hdiutil detach "$MOUNT_POINT" >> "$LOG_FILE" 2>&1; then
      log "Error unmounting DMG during cleanup"
    fi
  fi
}

# Function to process DMG files
process_dmg() {
  local DMG_PATH="$1"
  log "Working directory: $(pwd)"

  local DMG_DIR
  local DMG_NAME
  local MOUNT_POINT=""

  DMG_DIR=$(dirname "$DMG_PATH")
  DMG_NAME=$(basename "$DMG_PATH")

  if ! cd "$DMG_DIR"; then
    log "Error: Failed to change directory to $DMG_DIR"
    echo "Error: Failed to change directory. Please check the directory path."
    exit 1
  fi

  # Mount the DMG
  MOUNT_OUTPUT=$(hdiutil attach "$DMG_NAME" -nobrowse -noautoopen 2>&1)
  log "hdiutil attach output: $MOUNT_OUTPUT"
  MOUNT_POINT=$(echo "$MOUNT_OUTPUT" | grep "/Volumes" | awk -F '\t' '{ print $3 }' | sed 's/^[[:space:]]*//')

  if [ -z "$MOUNT_POINT" ]; then
    log "Failed to mount DMG: $DMG_PATH"
    return 1
  fi

  # Destination check
  if [ ! -d "$DESTINATION" ]; then
    log "Destination directory $DESTINATION does not exist."
    cleanup
    return 1
  fi

  # Prioritize .pkg if it exists
  PKG_FILE=$(find "$MOUNT_POINT" -name "*.pkg" -maxdepth 1)

  if [ -n "$PKG_FILE" ]; then
    cp -av "$PKG_FILE" "$DESTINATION" >> "$LOG_FILE" 2>&1
    copy_status=$?
    if [ $copy_status -ne 0 ]; then
      log "Failed to copy .pkg file from DMG: $DMG_PATH"
      cleanup
      return 1
    fi
  else
    # Application Extraction Attempt
    APP_NAME=$(find "$MOUNT_POINT" -name "*.app" -maxdepth 2 | head -n 1)

    if [ -n "$APP_NAME" ]; then
      cp -a "$APP_NAME" "$DESTINATION/" >> "$LOG_FILE" 2>&1
      copy_status=$?
      if [ $copy_status -ne 0 ]; then
        log "Failed to copy application from DMG: $DMG_PATH"
        cleanup
        return 1
      fi
    else
      log "Warning: Couldn't determine specific application. Copying all DMG contents."
      cp -a "$MOUNT_POINT/"* "$DESTINATION/" >> "$LOG_FILE" 2>&1
      copy_status=$?
      if [ $copy_status -ne 0 ]; then
        log "Failed to copy files from DMG: $DMG_PATH"
        cleanup
        return 1
      fi
    fi
  fi

  # Run cleanup function to un-mount the dmg 
  cleanup
  
  # Trash DMG (if possible)
  if command -v /opt/homebrew/bin/trash >/dev/null 2>&1; then
      /opt/homebrew/bin/trash "$DMG_PATH" && killall Finder
  else
      log "Trash command not found. DMG not deleted: $DMG_PATH"
  fi

  log "Processed DMG: $DMG_PATH"
}

# Check for --setup argument
if [ "$1" = "--setup" ]; then
  setup_configuration
fi

# Pre-load log file path for logging
if [ -f "$CONFIG_FILE" ]; then
  # shellcheck source=/dev/null
  source "$CONFIG_FILE"
else
  echo "Configuration file not found. Please run the script with --setup to configure."
  log "WARN Configuration file failed to load successfully."
  exit 1
fi

# Load and validate configuration for normal operations
load_and_validate_configuration

# Install cleanup trap 
trap cleanup EXIT

# Main processing logic
for file in "$@"; do
  if [[ "$file" == *.dmg ]]; then
    process_dmg "$file"
  fi
done

First: download the above script, editing the two variables DESTINATION and LOG_FILE accordingly (make a blank log file and store it somewhere)

Open Automator on macOS and select "Folder Action" -

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Select the folder you want the action to monitor for the .dmg files, then search "Run Shell Script" & drag it accordingly - then paste the following into the field:

/Users/username/delete_dmg_after_use.sh "$@"

(note: this should match where the above script is stored)

Then save the workflow and you should be good to go 🙂

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Visually this can be seen below: