#!/bin/bash
## I probably used bashisms here, so we run with bash

## This Script detects what dialog to use in an X session from (currently) 3 options,
## Kdialog, the KDE/Qt dialog
## Zenity, the Gnomw/GTK dialog
## Xdialog, the generic X dialog
# First we initialise our DIALOG variable, so if all check fail, we can tell
DIALOG=''
# DIALOGS is the list of dialog apps we want to check for
DIALOGS="kdialog zenity xdialog"

# Now we check that the user is in a GUI session
if [ -z $DISPLAY ]
   then echo "DISPLAY not set" >&2 # we post an error message to the terminal
   exit 1 # and exit here
fi

# Now we start checking for the dialog apps
for i in $DIALOGS
    do if [ -x /usr/bin/$i ] # Check the app exists (and is executable) 
          then DIALOG=$i     # if it exists, then set DIALOG to it
          break              # and stop checking, if it doesn't exist
       fi                    # then it moves to the next dialog to check.
done

if [ -z $DIALOG ] # If DIALOG wasn't set then we have no dialog app
then if [ -x /usr/bin/xmessage ] # we check for xmessage ( a basic text box installed with X)
        then xmessage "No dialog application was found.
You need one of kdialog (for Kubuntu),
zenity (for Ubuntu/Edubuntu/Xubuntu)
or xmessage (generic)." # and print a message for the user
    else echo "No dialog application was found.
You need one of kdialog (for Kubuntu),
zenity (for Ubuntu/Edubuntu/Xubuntu)
or xmessage (generic)." # if xmessage isn't installed (god knows why), then print the message to the terminal
    fi
 exit 1 # and die
fi