Remove/Delete a string of characters from filenames

I have a bunch of text files that end with the line www.thethinkfoundation.org, for example:

file1.www.thethinkfoundation.org.txt

file2.www.thethinkfoundation.org.txt . . .

file100.www.thethinkfoundation.org.txt

I wish to remove/delete www.thethinkfoundation.org

I tried the following command in a terminal to achieve it. It is:

for f in www.thethinkfoundation.org*; do mv "$f" "${f#thethinkfoundation.org}"; done

The result was:

file1..txt

file2..txt . . .

file100..txt

Thank you in advance for a solution that works.

P.S.: I do not wish to use the rename command. I am actually looking for one that works across Linux and *BSD distros. My preferred text editor is nano

Sub-string replacement based on Shell Parameter Expansion in bash and a few other shells as well can be achieved in two ways:

First, you can replace only the first occurrence(from left to right) of a pattern like so:

${var/pattern/replacement}

Second, you can replace all occurrences of a pattern like so:

${var//pattern/replacement}

Where var is the variable/parameter containing the string and pattern is the pattern that you wish to find and replace in that string and replacement is the replacement that you wish to substitute that pattern with which can be left empty as well i.e. ${var//pattern/} if you wish to just delete that pattern from the string.

Therefore, your desired solution would look like this:

for f in *www.thethinkfoundation.org*; do
    echo mv -n -- "$f" "${f//www.thethinkfoundation.org./}"
done

I added echo for a dry-run so that you can test it first and then take out echo and run it again to do the real work.