Shell Programming and Scripting

Need your help in creating regular expression for particular set. let say I have given two dates 20130623 to 20140625.

I need to create regular for the dates which fall in between above two dates.

A regular expression to be used by what?

Expanding on Don's question a bit -

There are different Regular expressions that work with different tools - for example: perl, grep, awk.

In order to answer your question we need to know what tool you want to use. There are "flavors" of regular expressions and they have differences.

Also, are you concerned about trapping "illegal" dates, like 20140230?

Looking at your requirement, you actually don't need a regular expression.
How would you find out if the dates between the said dates with regex !?
Your date format is YYYYMMDD, you might just need a numeric comparison to check if your date fall in between the given dates.

Note: As Chubler_XL said, the above solution trust on the fact that input is coming as a valid date with YYYYMMDD format. Otherwise, off-course you would need a regex check to validate your input date.

Please elaborate more.