Consider the need to use 'diff' to compare two files with many commented lines, such as system configuration files. (For example, the files could be /etc/cups/cups-files.conf.pacnew and /etc/cups/cups-files.conf.)
I would like to ignore differences of any lines that are commented out such as these:
< #DocumentRoot /usr/share/cups/doc --- > #DocumentRoot /usr/share/cups/doc-root
I only want to see differences of active (uncommented) lines.
(I would also like to ignore whitespace differences. I mention that for completeness in case the solution for the above interferes with using the the