zenity — Display dialogs from the command-line/shell scripts. Return user-inserted values or 1 if error. More

Display the default question dialog

zenity --question

Display an info dialog displaying a message

zenity --info --text "{{message}}"

Display a name/password form and output the data separated by ";" ("|" by default)

zenity --forms --add-entry "{{name_label}}" --add-password "{{password_label}}" --separator ";"

Display a file selection form in which the user can only select directories

zenity --file-selection --directory

Display a progress bar which updates its message every second and show a progress percent

{{(echo "#1"; sleep 1; echo "50"; echo "#2"; sleep 1; echo "100")}} | zenity --progress