How to modify a lot of html files at the same time?

I have thousands of HTML files that I would like to modify at the same time on a Fedora system. It would be to replace style.css by ../headers.css and to replace another long chain that you can see here : http://pastebin.com/PHAz8Q4C

Solution

I'd recommend using a tool like sed which can do text/regex replacements on a file.

Combining this with find and xargs is a good start to making it work on a large number of files.

So, for example, you could do something like

find -name "*.html" -print0 | xargs -0 sed -i 's#style.css#../headers.css#g'

Since there is no way to undo this operation, I would recommend making a backup of the files just in case (or use version control!)

EDIT: Guide on how to expand this to other search/replace terms (like your pastebin):

Same idea. Just make sure you escape everything properly. As an explanation that can get you further...

find finds all the html files
xargs runs the command after it on each file
sed does the replacement
-i tells sed to do it in place
s tells it to Substitute
style.css is what to replace
../headers.css is what to replace it with
and g tells it to replace all occurrences in the file.