Improve Bash Shell Scripts Using Dialog http://www.linuxjournal.com/article/2460 The "dialog" command offers an easy way to draw text-mode colored windows. These windows can contain text boxes, message boxes or different kinds of menus. There are even ways of using input from the user to modify the script behaviour. The current version of the dialog program is cdialog-0.9 and can be freely downloaded from Sunsite's /pub/Linux/utils/shell directory. Dialog uses the ncurses library, so it too must be installed. Some Linux distributions such as Slackware include the dialog program because of utilities which rely on it (setup, pkgtool). By the way, these utilities are great examples of using dialog. cdialog: dependencies: ncurses Debian/Ubuntu Install: apt-get install dialog Basic Usage: #!/bin/sh dialog --title "Dialog message box" --msgbox "\n Hello world !" 6 25 -------------------------------------------------------------------------------- List Directory Contents Script (--inputbox) #!/bin/sh # list the contents of a dir dialog --title "Dialog input box" --inputbox "Input directory:" 8 40 `pwd` 2>/tmp/dialog.ans if [ $? = 1 ]; then rm -f /tmp/dialog.ans clear exit 0 fi ANS=`cat /tmp/dialog.ans` ls -al $ANS > /tmp/dialog.ans dialog --no-shadow --title "listing of"$ANS --textbox /tmp/dialog.ans 25 78 clear rm -f /tmp/dialog.ans exit 0 The text box allows navigating with the arrow keys or home/end/pgup/pgdown keys and even has simple searching facilities. Typing / while the text box is displayed causes another window to appear, which prompts the user for a string to be searched forward in the file. Typing ? performs reverse searching, just as for the less pager. The first line containing the string is displayed at the top of the text box. What if the directory name is wrong? The shell script will not complain, but will show an empty text box since there are no files in a nonexistent directory. To solve this problem, a check is made to see if the specified directory exists. Actually, the ls command returns an exit status of 0 if the directory exists, and 1 if it doesn't. Thus, the script can be modified by adding these lines: ls -al $ANS > /tmp/dialog.ans 2>/dev/null if [ $? = 1 ]; then clear echo no such directory exit 1 fi First, the ls line is changed, redirecting standard error to /dev/null. This means no error messages from ls will appear on the screen. Then, if the exit status ($?) is 1, the script will exit with an error message. -------------------------------------------------------------------------------- This script can be made even more useful by allowing the user to examine more directories before the script exits. #!/bin/sh # Lists the contents of a directory while [ 0 ]; do dialog --title "Dialog input box" --inputbox "Input directory or \n press <Cancel> to exit" 9 40 `pwd` 2>/tmp/dialog.ans if [ $? = 1 ]; then clear rm -f /tmp/dialog.ans # don't litter ! exit 0 fi ANS=`cat /tmp/dialog.ans` ls -al $ANS > /tmp/dialog.ans 2>/dev/null if [ $? = 1 ]; then dialog --title "Error" --msgbox "no such directory" 5 40 continue fi dialog --no-shadow --title "listing of "$ANS -textbox /tmp/dialog.ans 25 78 done A few changes have been made. First, the entire script has been included in a while-do loop which is always true. This allows it to run more than once. Now the only way of exiting the script (besides typing ctrl-c) is by selecting the Cancel button in the dialog input box. The second change is the introduction of a message box which will be displayed when the ls command returns an exit status of 1. The command continue deserves a special comment. Its meaning is to skip the current iteration of the while loop (i.e., the part which shows the text box) and start a new one. Thus, after the error message, the user will again see the input box, prompting for another directory name. -------------------------------------------------------------------------------- The menu box is produced by running dialog with the --menu option with the format: dialog --menu tag2 item2... This option displays a box with two buttons (OK and Cancel) and a menu consisting of one or more lines. Each line has a "tag" (a number or word) and an "item", which is usually text describing the menu entry. When a user selects an item and then clicks on the OK button, the corresponding tag is printed on STDERR. Also, the exit status of dialog is 0 for the OK button being selected and 1 for the Cancel button. Menu boxes are useful in that they allow the user to choose from several fixed alternatives. For example, when producing a LaTeX document, three steps must be taken: editing the source file with a word processor, compiling it with LaTeX and viewing the resulting .dvi file. It is easy to build a shell script to do these steps. (See Listing 3 which assumes the text editor is jed, the .dvi file viewer is dvisvga and both are in the path.) The complete script is again included in a “while” loop for the purpose of making it work more than one time. The only way to exit this script is by selecting the "Cancel" button in the first menu box. Otherwise, the user has to choose between three alternatives: Edit a text file. Compile a LaTeX file. View a .dvi file. The answer is stored in the file /tmp/ans and retrieved in the variable R. If the user chooses to edit a file, a new dialog box appears. It is an input box and prompts for a file name. The answer goes into the variable F. Then the script checks whether the file exists and runs the command: jed $F # where $F is the name of the file If the file does not exist, it is either a new one or a typing error. To distinguish between these two possibilities, a yes/no dialog box is provided. The general format of such a box is: --yesno The box has two buttons, YES and NO. The text is usually a question, which the user answers by selecting a button. If YES, $? (the exit status of the dialog command) is 0; if NO, $? is 1. In Listing 3, if the answer is YES, the text editor is invoked; if NO, the script returns to the main menu through the continue command. The other two choices work in the same way, the only difference being the commands for processing the file with LaTeX or for viewing the resulting DVI file: latex $F dvisvga $F Several other dialog boxes are available, such as the checklist or the radiolist; however, their use is quite similar to that of the menu box. -------------------------------------------------------------------------------- The following is an example of the --guage dialog box. This is used to graphically display a percentage. The syntax is: dialog --guage Once started, the guage box keeps reading percent values from STDIN until an EOF is reached and changes the display accordingly. Here is a simple (but not very useful) guage script: #!/bin/bash { for I in 10 20 30 40 50 60 70 80 90 80 70 60 50 40 30 20 10 0; do echo $I sleep 1 done echo; } | dialog --guage "A guage demo" 6 70 0 Copy this into a file, give it execute permission, run and enjoy! The first part of the script (included in braces) is a group command. Every second it sends one of the listed values to the guage dialog box. The final echo command is used to terminate the dialog box. -------------------------------------------------------------------------------- #!/bin/sh #script for editing, proccesing and viewing LaTeX documents while [ 0 ]; do dialog --title "Dialog menu box" --menu "Choose one of the following or press <Cancel> to exit" 11 40 3 \ "1" "Edit a text file" \ "2" "Compile a latex file" \ "3" "View a .dvi file" 2>/tmp/ans if [ $? = 1 ]; then rm -f /tmp/ans clear exit 0 fi R="`cat /tmp/ans`" if [ $R = "1" ]; then dialog --title "Dialog input box" --inputbox "Please input file name:" 8 40 $F 2>/tmp/ans if [ $? = 1 ]; then continue fi F="`cat /tmp/ans`" if [ -f $F ]; then jed $F else # if the file does not exist... dialog --title "Dialog yesno box" --yesno "\n Is this a new file ?" 6 40 if [ $? = 0 ]; then jed $F else continue fi fi elif [ $R = "2" ]; then dialog --title "Choose file" --inputbox "Please input file name:" 8 40 $F 2>/tmp/ans if [ $? = 1 ]; then continue fi F="`cat /tmp/ans`" if [ -e $F ]; then clear latex $F else # if the file does not exist... dialog --title "Dialog message box" --msgbox "\n File not found" 6 30 continue fi elif [ $R = "3" ]; then dialog --title "Dialog input box" --inputbox "Please input file name:" 8 40 $F 2>/tmp/ans if [ $? = 1 ]; then continue fi F="`cat /tmp/ans`" if [ -f $F ]; then clear tmview $F else # File not found... dialog --title "Dialog message box" --msgbox "\n File not found" 6 30 continue fi fi done -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- user@vmwarex[~] $ dialog cdialog (ComeOn Dialog!) version 1.1-20070604 Copyright 2000-2006,2007 Thomas E. Dickey This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. * Display dialog boxes from shell scripts * Usage: dialog <options> { --and-widget <options> } where options are "common" options, followed by "box" options Special options: [--create-rc "file"] Common options: [--ascii-lines] [--aspect <ratio>] [--backtitle <backtitle>] [--begin <y> <x>] [--cancel-label <str>] [--clear] [--colors] [--cr-wrap] [--default-item <str>] [--defaultno] [--exit-label <str>] [--extra-button] [--extra-label <str>] [--help-button] [--help-label <str>] [--help-status] [--ignore] [--input-fd <fd>] [--insecure] [--item-help] [--keep-tite] [--keep-window] [--max-input <n>] [--no-cancel] [--no-collapse] [--no-kill] [--no-label <str>] [--no-lines] [--no-shadow] [--ok-label <str>] [--output-fd <fd>] [--print-maxsize] [--print-size] [--print-version] [--separate-output] [--separate-widget <str>] [--shadow] [--single-quoted] [--size-err] [--sleep <secs>] [--stderr] [--stdout] [--tab-correct] [--tab-len <n>] [--timeout <secs>] [--title <title>] [--trace <file>] [--trim] [--version] [--visit-items] [--yes-label <str>] Box options: --calendar <text> <height> <width> <day> <month> <year> --checklist <text> <height> <width> <list height> <tag1> <item1> <status1>... --dselect <directory> <height> <width> --editbox <file> <height> <width> --form <text> <height> <width> <form height> <label1> <l_y1> <l_x1> <item1> <i_y1> <i_x1> <flen1> <ilen1>... --fselect <filepath> <height> <width> --gauge <text> <height> <width> [<percent>] --infobox <text> <height> <width> --inputbox <text> <height> <width> [<init>] --inputmenu <text> <height> <width> <menu height> <tag1> <item1>... --menu <text> <height> <width> <menu height> <tag1> <item1>... --mixedform <text> <height> <width> <form height> <label1> <l_y1> <l_x1> <item1> <i_y1> <i_x1> <flen1> <ilen1> <itype>... --mixedgauge <text> <height> <width> <percent> <tag1> <item1>... --msgbox <text> <height> <width> --passwordbox <text> <height> <width> [<init>] --passwordform <text> <height> <width> <form height> <label1> <l_y1> <l_x1> <item1> <i_y1> <i_x1> <flen1> <ilen1>... --pause <text> <height> <width> <seconds> --progressbox <height> <width> --radiolist <text> <height> <width> <list height> <tag1> <item1> <status1>... --tailbox <file> <height> <width> --tailboxbg <file> <height> <width> --textbox <file> <height> <width> --timebox <text> <height> <width> <hour> <minute> <second> --yesno <text> <height> <width> Auto-size with height and width = 0. Maximize with height and width = -1. Global-auto-size if also menu_height/list_height = 0.