Shell Programming and Scripting

Hi friends,

I want to make one script and i need to sort me out for some logic means how i can make this script.

in whole day i got files from my lots of client which is xml files and condition is one client can send lots of files as much as he want.

at the end of day we make one file in which all xml files are concatenate. and when that file reached in our server , all small xml files deleted from directory and only one file present which has lots of clients xml for that day.

Now sometime we need xml files for that particular clients. so we grep with client id in that large xml files but concern is grep only gave output for that particular line, i want extract whole xml for that particular client from one biggest file .

all xml files start with <doctype> and end with </doctype>.

can some one suggest me logic how i can do this extraction of xml for that particular client which may have one or many xml files in that biggest files.

<client_id>????</clinet_id>

Please post some more representative input data, not a mockup, and show the output you want from it.