Substring using bat command

>set fullname=c:\mypath\oldfile
>set changedname=%fullname:oldfile=newfile%
>echo %changedname%
c:\mypath\newfile

> set fullname=c:\mypath\oldfile
> set pathonly=%fullname:oldfile=%
> echo %pathonly%
c:\mypath\ 

Ref:http://stackoverflow.com/questions/2690382/substring-using-bat-command