What is regular expressions ?? I am not understand its programs as well as concept

Answer 1

You can use python to communicate with server and keep only the data you want by filtering it through RegEx

Answer 2

If you want to get all resources of html page:

(?<=(src|href)=")(.|\n)+?(?=")

Answer 3

(?<=then)S?earch(?=[Goo]gle)…*?

Answer 4

Regular expressions, despite how complex they may seem, are used to make it easy to match patterns in strings. It's purpose is basically to tell a program exactly what to search for.

Imagine that you have a .txt file with thousands of words, and that you want to search for all the integers in this file, you could type (in a Linux terminal window):
egrep -o "[0-9]+" file.txt (egrep is a great command).
The syntax may differ slightly depending on what program or language you're using, for example java and c# have similar regex handling.

Answer 5

you mean all this are regular expressions ?..... so how to use it in programs n for what conditions ?