https://stackoverflow.com/questions/7035/how-to-show-a-gui-message-box-from-a-bash-script-in-linux
  ( see also:   http://alternativeto.net/software/zenity/ )


- notify-send
notify-send "My name is bash and I rock da house"

- zenity
zenity --info --text="Calculation complete"
zenity --file-selection --title="choose mount-script"
my_variable=$(zenity --entry --text="What's my variable:")
my_date=$(zenity --calendar)



- gxmessage
gxmessage "my text"

- xmessage
xmessage -buttons Ok:0,"Not sure":1,Cancel:2 -default Ok -nearmouse "Is xmessage enough for the job ?" -timeout 10

- kdialog 
kdialog --error "Some error occurred"

- YAD
Yad allows you to display GTK+ dialog boxes from command line or shell
scripts. It is similar to Zenity but with more dialog types and options.

echo My text | yad \
--text-info \
--width=400 \
--height=200

yad --file-selection --width=1000 --height=250

yad \
--title="Desktop entry editor" \
--text="Simple desktop entry editor" \
--form \
--field="Type:CB" \
--field="Name" \
--field="Generic name" \
--field="Comment" \
--field="Command:FL" \
--field="Icon" \
--field="In terminal:CHK" \
--field="Startup notify:CHK" "Application" "Name" "Generic name" "This is the comment" "/usr/bin/yad" "yad" FALSE TRUE \
--button="WebUpd8:2" \
--button="gtk-ok:0" \
--button="gtk-cancel:1"

- xterm
xterm -e bash -c 'echo "this is the message";echo;echo -n "press enter to continue "; stty sane -echo;answer=$( while ! head -c 1;do true ;done);'