#!/bin/bash
TMPFILE="/tmp/filename.txt"
dialog --title "Input - Delete a file" --backtitle "Welcome to Linux delete" --inputbox "Enter delete file name" 8 60 2>$TMPFILE
sel=$?
out=$(cat $TMPFILE)
if [ ! -f $out ]; then
  echo "Fie $out does not exists"
  exit 1
else
  case $sel in
   0) /bin/rm $out; echo "File $out has been deleted";;
   1) echo "You pressed cancel";;
   255) echo "You pressed ESC";;
  esac
fi
/bin/rm $TMPFILE