Need help with sed to fix migrated web site links (part II)

Question

I thought I had this fixed, but I didn't, so starting over:
I'm moving my web files from one host to another, and have backed up my directory called WEB into my user downloads folder.  The site is dead simple, mostly links within the site, pages primarily text with some links to my photos posted on flickr, and a few outside links.  I want to avoid opening/replacing/saving a hundred or more files to fix the links from "http://www.old_domain_name/user/my_username" to "http://my_new_domain_name"
A friend suggested the following scripts to do this
  mkdir fix_urls
  cd fix_urls
  cp -r <wherever>/WEB .
  cd WEB
  xargs -0 egrep -i  old_domain_name $(find * -name "*.html" -print0) > ../to_fix
  cd ..
  less to_fix
to see what needs changing, but after I've created and moved to WEB, the xargs command results in a zero kb file called to_fix appearing in WEB, and nothing else happens....and the prompt in terminal (myusername$) doesn't reappear.
I tried his part II anyway:
  mkdir new_web
  while read filename; do
      sed 's/\/www.old_domain_name/user/my_username/\/my_new_domain_name/' < WEB/$filename > new_web/$filename
  done
  diff -r WEB new_web > what_i_did
  less what_i_did
and after the 'done', I get again....nothing.  No new cursor gray rectangle, no new prompt, haven't even gotten to the last bit of diff to review the changes.
Any tips on what fundamental bone-headed thing I'm doing wrong?
and I got this helpful answer which seemed to have solved it, but didn't entirely:
This solved my question by X423424X  on Jul 1, 2012 1:23 AM
I want to avoid opening/replacing/saving a hundred or more files to fix the links from "http://www.old_domain_name/user/my_username" to "http://my_new_domain_name"
If that's all you want to do then here's the pertinent sed command to do it:
sed -e 's,www.old_domain_name/user/my_username,my_new_domain_name,'
Syntax is a bit simpler when you don't use slashes as the sed substitute delimiters.  You can use anything.  Here I used commas.
I got excited too quickly after the first file I clicked looked correct--the first file in the subdirectory.
I see no indication in terminal that the process is going or ending--no sense of when I can close terminal and move on.
Checking the directory in finder shows no updates to 'date modified' for any of the files.
So how do I know if it is in progress, or done working, aside from opening random files to see if they're 'done'?
I've got three subfolders inside one folder (my WEB folder), and it looks like only the first file of the first subdirectory got repaired.

Answer 1

Here is a bash script to interate through all files in a folder of a given extension.
#!/bin/bash
# be sure to use Unix lineends -- linefeed \n
# Use TextWrangle for editing.  It's free.
# http://www.barebones.com/products/TextWrangler/
# or nano in the terminal
# to make this file -- listFile.bash runable do:
# chmod u+x listFile.bash
# debug info
export PS4='+(${BASH_SOURCE}:${LINENO}):'
# remove the leading # in the line below to show debug info
# set -o xtrace
# first comes the directory/folder you want to search
# -name do a case independent search for all file ending
#       with the extension .txt
find /Users/mac/Desktop/iMac -iname "*.txt" | while read file
do
    echo
    echo "file to process is = " $file
    # replace the list command with your command.
    # You will need to place a $ in front of file
    # To avoid problems with blanks & other characters,
    # put " around $file, your variable.
    ls -l "$file"
done
mac $ chmod u+x /Users/mac/Desktop/listFiles.bash
mac $ /Users/mac/Desktop/listFiles.bash
file to process is =  /Users/mac/Desktop/iMac/bash/pdisk-l.txt
-rw-r--r--   1 mac  staff  20915 Feb  4  2009 /Users/mac/Desktop/iMac/bash/pdisk-l.txt
file to process is =  /Users/mac/Desktop/iMac/comments on new forum software.txt
-rw-r--r--   1 mac  staff  1966 May 26  2011 /Users/mac/Desktop/iMac/comments on new forum software.txt
file to process is =  /Users/mac/Desktop/iMac/hidden mac os files.txt
-rw-r--r--   1 mac  staff  1499 Jul  1 17:01 /Users/mac/Desktop/iMac/hidden mac os files.txt
file to process is =  /Users/mac/Desktop/iMac/key combinations.txt
-rw-r--r--   1 mac  staff  2547 Aug 24  2011 /Users/mac/Desktop/iMac/key combinations.txt
file to process is =  /Users/mac/Desktop/iMac/nvram -p.txt
-rw-r--r--   1 mac  staff  1248 Feb  1  2011 /Users/mac/Desktop/iMac/nvram -p.txt
file to process is =  /Users/mac/Desktop/iMac/reset mac Open Firmware.txt
-rw-r--r--   1 mac  staff  7876 Jun 25 21:56 /Users/mac/Desktop/iMac/reset mac Open Firmware.txt
mac $