Linux Shell Scripting Cookbook - Third Edition

How it works...

The image downloader script reads an HTML page, strips out all tags except <img>, parses src="URL" from the <img> tag, and downloads them to the specified directory. This script accepts a web page URL and the destination directory as command-line arguments.

The [ $# -ne 3 ] statement checks whether the total number of arguments to the script is three, otherwise it exits and returns a usage example. Otherwise, this code parses the URL and destination directory:

while [ -n "$1" ] 
do  
  case $1 in 
  -d) shift; directory=$1; shift ;; 
   *) url=${url:-$1}; shift;; 
esac 
done 

The while loop runs until all the arguments are processed. The shift command shifts arguments to the left so that $1 will take the next argument's value; that is, ...