rename [from] [to] [files]
So if you wanted to rename all .txt files to .html you would do: rename .txt .html *.txt
You can also use perl command line (can't find the exact code, but this will create a "backup" of the file:
perl -p -i.html *.txt
only problem is that it would name it file1.txt.html, I used to have a command line code to do this, can't find it now.
if you are using Windows, rename from DOS/Command Prompt (rename /? for more info).
Scott Geiger