I'd like to extract content of old
.chm file into individual html files.
Is there an app or command line tool for this?
Perhaps http://echoone.com/filejuicer/formats/chm will do the job for you.
FWIW, my chm to HTML workflow differs though. I use iCHM app (http://www.macupdate.com/app/mac/28171/ichm) for OS X to convert chm to PDF to preserve formatting. After editing it (using Adobe Acrobat) as necessary, only then do I convert to HTML.