Many Bash scripts do not need interfaces. They are run by admins, who are comfortable at the command line. However, if a script is used by everyday users, it may be more friendly if it uses a dialog box for input and messages. For over 25 years, a leading command for boxes has been dialog [1], which can be called from a script so that users can enter input in an ncurses interface. It then returns them to the script when they exit.

The command structure of dialog is somewhat unusual (Listing 1). In addition to the appearance of options in two separate places, note the quotation marks around the text, and the order of height, width, and other box type options. Height is expressed as the number of lines and width as the number of monospaced characters.

The design of the resulting box varies with the options selected. However, it will always have text and may have buttons (such as Yes, No, Help, or OK) or radio buttons for making selections. It may also have a back title for easy identification. When necessary, the box can be navigated by using arrow keys, and it is not supported by a mouse (Figure 1). Once a selection is made, then generally the script will continue with if/then/else statements that correspond to each selection.

[...]