Linux Shell Scripting Cookbook - Third Edition

How to do it...

This Bash script combines different commands, to track changes in a web page:

#!/bin/bash 
#Filename: change_track.sh 
#Desc: Script to track changes to webpage 

if [ $# -ne 1 ]; 
then  
  echo -e "$Usage: $0 URL\n" 
  exit 1; 
fi 

first_time=0 
# Not first time 

if [ ! -e "last.html" ]; 
then 
  first_time=1 
  # Set it is first time run 
fi 

curl --silent $1 -o recent.html 

if [ $first_time -ne 1 ]; 
then 
  changes=$(diff -u last.html recent.html) 
  if [ -n "$changes" ]; 
  then 
    echo -e "Changes:\n" 
    echo "$changes" 
  else 
    echo -e "\nWebsite has no changes" 
  fi 
else 
  echo "[First run] Archiving.." 

fi 


cp recent.html last.html 

Let's look at the output of the track_changes.sh script on a website you control. First we'll see the output when a web page is unchanged, ...