curl wget - How to ignore the HTML Tag and headers [duplicate]

If you just want to dump the page in printable form, that's doable with a text-browser (such as lynx, w3m, elinks). Those have a "-dump" option.

Here's the beginning of that page with "lynx -dump":

   [1]LINFO

                               The cat Command

   cat is one of the most frequently used [2]commands on [3]Unix-like
   [4]operating systems. It has three related functions with regard to
   text files: displaying them, combining copies of them and creating new
   ones.

   cat's general syntax is

     cat [options] [filenames] [-] [filenames]

   The square brackets indicate that the enclosed items are optional.