sed + remove “#” and empty lines with one sed command

Question

how to remove comment lines (as # bal bla ) and empty lines (lines without charecters) from file with one sed command?

THX lidia

Answer 1

On (one of) my linux boxes, sed understands extended regular expressions with the -r option, so:

sed -r '/(^\s*#)|(^\s*$)/d' squid.conf.installed

is very useful for showing all non-blank, non comment lines. The regex matches either start of line followed by zero or more spaces or tabs followed by either a hash or end of line, and deletes those matching lines from the input.