install-notify.sh

set -e

DIR="$( cd "$( dirname "$0" )" && pwd )"
TARGET_DIR="$HOME/.config/google-chrome/NativeMessagingHosts"
# If you use Chromium, uncomment the next line, and comment the previous line
# TARGET_DIR="$HOME/.config/chromium/NativeMessagingHosts"

HOST_NAME=com.initiated.chrome_libnotify_notifications

# Create directory to store native messaging host.
mkdir -p $TARGET_DIR

# Copy native messaging host manifest.
cp "$DIR/$HOST_NAME.json" "$TARGET_DIR"

# Update host path in the manifest.
HOST_PATH=$DIR/invoke_notify
ESCAPED_HOST_PATH=${HOST_PATH////\\/}
sed -i -e "s/HOST_PATH/$ESCAPED_HOST_PATH/" $TARGET_DIR/$HOST_NAME.json

# Set permissions for the manifest so that all users can read it.
chmod o+r $TARGET_DIR/$HOST_NAME.json

echo Native messaging host $HOST_NAME has been installed.

I am getting:

$ sh ./install-notify.sh 
./install-notify.sh: 18: ./install-notify.sh: Bad substitution