Dialog Utility
A Dialog Box is a temporary window an application runs to convey important information to the users. These dialog boxes can be used to display warnings, errors, and also any additional inputs needed by the system from End Users.
Dialog Utility — A utility for creating text based dialog boxes within scripts:
True to the Unix tradition of writing general-purpose tools that work together, dialog allows creating text- based color dialog boxes from any shell script language. It supports eight types of dialogs:
Yes/no boxes
Menu boxes
Input boxes
Message boxes
Text boxes
Info boxes
Checklist boxes
Radiolist boxes
Most calls to dialog are in a similar format: an optional title, the dialog type, the text to be displayed, and the height and width (in characters) of the dialog box. Additional parameters specific to each menu type follow. Let’s have a brief look at each of the available types.
dialog --title "Message" --msgbox "Hello, world" 5 20
This example creates a message box with the title Message, containing the greeting Hello, world!. The box is 5 lines high and 20 characters wide, with the message nicely centered in the box. An OK button appears at the bottom; pressing <enter> dismisses the menu.
The yesno menu is very similar to our first example:
dialog --title "Message" --yesno "Are you having\ fun?" 6 25
If you try this example, you will see that there are now two buttons at the bottom, labeled Yes and No. You can select between the buttons using the cursor keys (or <tab>) and make your selection by pressing <enter>. The exit status returned to the shell will be 0 if Yes is chosen and 1 if a No selection is made
You may wish to try experimenting with the height and width parameters. If the width is less than the string length, the string is wrapped around (at word boundaries). If you make the dialog box too small, then characters will be lost
We previously saw the message box. The infobox is similar except that it does not wait for the user to select an OK button. This is useful for displaying a message while an operation is going on. Here is an example:
dialog --infobox "Please wait" 10 30 ; sleep 4
The inputbox allows a user to enter a string. The usual editing keys can be used, and the text field scrolls if necessary. After the user enters the data, it is written to standard error (or more commonly redirected to a file as in this example):
dialog --inputbox "Enter your name:" 8 40 2>answer
The textbox type is a simple file viewer; it takes a filename as a parameter:
dialog --textbox /etc/profile 22 70
The usual movement keys work here: the cursor keys, Page Up, Page Down, Home, etc. You can exit by pressing <esc> or <enter>.
The menu type allows creating a menu of choices from which the user can choose. The format is
dialog --menu <text> <height> <width> <menu-height> [<tag><item>]
Each menu entry consists of a tag string and an associated item string, both of which are displayed. The user can make a choice using the cursor keys and pressing <enter>. The selected tag is written to standard error. Here is a simple example:
dialog --menu "Choose one:" 10 30 3 1 red 2 green 3 blue 2>ans1
The next type is the checklist. The user is presented with a list of choices and can toggle each one on or off individually using the space bar:
CHECKLIST
dialog --checklist "Choose OS:" 10 40 5 \
1 Linux on\
2 Solaris off\
3 "HP UX" off\
4 AIX off 2>ans2
The third field in each choice is the initial state; -either on or off. The last type is the radiolist, essentially the same as the checklist except that the user must make one choice from a list of mutually exclusive options. The radiolist type, and the alternate form of title show here, were introduced in version 0.4 of dialog.
dialog --backtitle "CPU Selection" \
--radiolist "Select CPU type:" 10 40 4 \
1 386SX off \
2 386DX on\
3 486SX off\
4 486DX off