If you have a script that is generating the text file, then you COULD also generate a separate html file at the same time.
Further info on this can be found in this post .
As far as starting a web browser that brings up a specific page from the command line, I don't know if that can be done. UNIX isn't like Windows. If you double click on a html document or jpeg, Windows launches a browser to open it. I can't find any documentation on doing the same from the command line in UNIX (or in DOS - opening or giving the type command to a html doc will just type it out - not open a browser).
cat > filename.html opens the file for input, not to be read. if you just want to read the file do "cat filename.html" or "more filename.html" to view the contents.