kdialog
Show KDE dialog boxes from within shell scripts.
TLDR
Open a dialog box displaying a specific message
$ kdialog --msgbox "[message]" "[optional_detailed_message]"
Open a question dialog with a yes and no button, returning 0 and 1, respectively
$ kdialog --yesno "[message]"
Open a warning dialog with a yes, no, and cancel button, returning 0, 1, or 2 respectively
$ kdialog --warningyesnocancel "[message]"
Open an input dialog box and print the input to stdout when OK is pressed
$ kdialog --inputbox "[message]" "[optional_default_text]"
Open a dialog to prompt for a specific password and print it to stdout
$ kdialog --password "[message]"
Open a dialog containing a specific dropdown menu and print the selected item to stdout
$ kdialog --combobx "[message]" "[item1]" "[item2]" "[...]"
Open a file chooser dialog and print the selected file's path to stdout
$ kdialog --getopenfilename
Open a progressbar dialog and print a DBUS reference for communication to stdout
$ kdialog --progressbar "[message]"